@article{abbott_abe_acernese_ackley_adhikari_adhikari_adkins_adya_affeldt_agarwal_et al._2022, title={All-sky search for continuous gravitational waves from isolated neutron stars using Advanced LIGO and Advanced Virgo O3 data}, volume={106}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.106.102008}, DOI={10.1103/PhysRevD.106.102008}, abstractNote={We present results of an all-sky search for continuous gravitational waves which can be produced by spinning neutron stars with an asymmetry around their rotation axis, using data from the third observing run of the Advanced LIGO and Advanced Virgo detectors. Four different analysis methods are used to search in a gravitational-wave frequency band from 10 to 2048 Hz and a first frequency derivative from $\ensuremath{-}{10}^{\ensuremath{-}8}$ to ${10}^{\ensuremath{-}9}\text{ }\text{ }\mathrm{Hz}/\mathrm{s}$. No statistically significant periodic gravitational-wave signal is observed by any of the four searches. As a result, upper limits on the gravitational-wave strain amplitude ${h}_{0}$ are calculated. The best upper limits are obtained in the frequency range of 100 to 200 Hz and they are $\ensuremath{\sim}1.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}25}$ at 95% confidence level. The minimum upper limit of $1.10\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}25}$ is achieved at a frequency 111.5 Hz. We also place constraints on the rates and abundances of nearby planetary- and asteroid-mass primordial black holes that could give rise to continuous gravitational-wave signals.}, number={10}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abe, H. and Acernese, F. and Ackley, K. and Adhikari, N. and Adhikari, R. X. and Adkins, V. K. and Adya, V. B. and Affeldt, C. and Agarwal, D. and et al.}, year={2022}, month={Nov} }
 @article{abbott_abe_acernese_ackley_adhikari_adhikari_adkins_adya_affeldt_agarwal_et al._2022, title={All-sky search for gravitational wave emission from scalar boson clouds around spinning black holes in LIGO O3 data}, volume={105}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.105.102001}, DOI={10.1103/PhysRevD.105.102001}, abstractNote={This paper describes the first all-sky search for long-duration, quasimonochromatic gravitational-wave signals emitted by ultralight scalar boson clouds around spinning black holes using data from the third observing run of Advanced LIGO. We analyze the frequency range from 20 to 610 Hz, over a small frequency derivative range around zero, and use multiple frequency resolutions to be robust towards possible signal frequency wanderings. Outliers from this search are followed up using two different methods, one more suitable for nearly monochromatic signals, and the other more robust towards frequency fluctuations. We do not find any evidence for such signals and set upper limits on the signal strain amplitude, the most stringent being $\ensuremath{\approx}{10}^{\ensuremath{-}25}$ at around 130 Hz. We interpret these upper limits as both an ``exclusion region'' in the boson mass/black hole mass plane and the maximum detectable distance for a given boson mass, based on an assumption of the age of the black hole/boson cloud system.}, number={10}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abe, H. and Acernese, F. and Ackley, K. and Adhikari, N. and Adhikari, R. X. and Adkins, V. K. and Adya, V. B. and Affeldt, C. and Agarwal, D. and et al.}, year={2022}, month={May} }
 @article{abbott_abbott_acernese_ackley_adams_adhikari_adhikari_adya_affeldt_agarwal_et al._2022, title={All-sky, all-frequency directional search for persistent gravitational waves from Advanced LIGO’s and Advanced Virgo’s first three observing runs}, volume={105}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.105.122001}, DOI={10.1103/PhysRevD.105.122001}, abstractNote={We present the first results from an all-sky all-frequency (ASAF) search for an anisotropic stochastic gravitational-wave background using the data from the first three observing runs of the Advanced LIGO and Advanced Virgo detectors. Upper limit maps on broadband anisotropies of a persistent stochastic background were published for all observing runs of the LIGO-Virgo detectors. However, a broadband analysis is likely to miss narrowband signals as the signal-to-noise ratio of a narrowband signal can be significantly reduced when combined with detector output from other frequencies. Data folding and the computationally efficient analysis pipeline, PyStoch, enable us to perform the radiometer map-making at every frequency bin. We perform the search at 3072 HEALPix equal area pixels uniformly tiling the sky and in every frequency bin of width $1/32\text{ }\text{ }\mathrm{Hz}$ in the range 20--1726 Hz, except for bins that are likely to contain instrumental artefacts and hence are notched. We do not find any statistically significant evidence for the existence of narrowband gravitational-wave signals in the analyzed frequency bins. Therefore, we place 95% confidence upper limits on the gravitational-wave strain for each pixel-frequency pair, the limits are in the range $(0.030\ensuremath{-}9.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}24}$. In addition, we outline a method to identify candidate pixel-frequency pairs that could be followed up by a more sensitive (and potentially computationally expensive) search, e.g., a matched-filtering-based analysis, to look for fainter nearly monochromatic coherent signals. The ASAF analysis is inherently independent of models describing any spectral or spatial distribution of power. We demonstrate that the ASAF results can be appropriately combined over frequencies and sky directions to successfully recover the broadband directional and isotropic results.}, number={12}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, N. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and Agarwal, D. and et al.}, year={2022}, month={Jun} }
 @article{abbott_abbott_acernese_ackley_adams_adhikari_adhikari_adya_affeldt_agarwal_et al._2022, title={Constraints on dark photon dark matter using data from LIGO’s and Virgo’s third observing run}, volume={105}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.105.063030}, DOI={10.1103/PhysRevD.105.063030}, abstractNote={We present a search for dark photon dark matter that could couple to gravitational-wave interferometers using data from Advanced LIGO and Virgo's third observing run. To perform this analysis, we use two methods, one based on cross-correlation of the strain channels in the two nearly aligned LIGO detectors, and one that looks for excess power in the strain channels of the LIGO and Virgo detectors. The excess power method optimizes the Fourier Transform coherence time as a function of frequency, to account for the expected signal width due to Doppler modulations. We do not find any evidence of dark photon dark matter with a mass between $m_{\rm A} \sim 10^{-14}-10^{-11}$ eV/$c^2$, which corresponds to frequencies between 10-2000 Hz, and therefore provide upper limits on the square of the minimum coupling of dark photons to baryons, i.e. $U(1)_{\rm B}$ dark matter. For the cross-correlation method, the best median constraint on the squared coupling is $\sim2.65\times10^{-46}$ at $m_{\rm A}\sim4.31\times10^{-13}$ eV/$c^2$; for the other analysis, the best constraint is $\sim 2.4\times 10^{-47}$ at $m_{\rm A}\sim 5.7\times 10^{-13}$ eV/$c^2$. These limits improve upon those obtained in direct dark matter detection experiments by a factor of $\sim100$ for $m_{\rm A}\sim [2-4]\times 10^{-13}$ eV/$c^2$, and are, in absolute terms, the most stringent constraint so far in a large mass range $m_A\sim$ $2\times 10^{-13}-8\times 10^{-12}$ eV/$c^2$.}, number={6}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, N. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and Agarwal, D. and et al.}, year={2022}, month={Mar} }
 @article{abbott_abe_acernese_ackley_adhikari_adhikari_adkins_adya_affeldt_agarwal_et al._2022, title={First joint observation by the underground gravitational-wave detector KAGRA with GEO 600}, volume={2022}, ISSN={2050-3911}, url={http://dx.doi.org/10.1093/ptep/ptac073}, DOI={10.1093/ptep/ptac073}, abstractNote={Abstract We report the results of the first joint observation of the KAGRA detector with GEO 600. KAGRA is a cryogenic and underground gravitational-wave detector consisting of a laser interferometer with 3 km arms, located in Kamioka, Gifu, Japan. GEO 600 is a British–German laser interferometer with 600 m arms, located near Hannover, Germany. GEO 600 and KAGRA performed a joint observing run from April 7 to 20, 2020. We present the results of the joint analysis of the GEO–KAGRA data for transient gravitational-wave signals, including the coalescence of neutron-star binaries and generic unmodeled transients. We also perform dedicated searches for binary coalescence signals and generic transients associated with gamma-ray burst events observed during the joint run. No gravitational-wave events were identified. We evaluate the minimum detectable amplitude for various types of transient signals and the spacetime volume for which the network is sensitive to binary neutron-star coalescences. We also place lower limits on the distances to the gamma-ray bursts analyzed based on the non-detection of an associated gravitational-wave signal for several signal models, including binary coalescences. These analyses demonstrate the feasibility and utility of KAGRA as a member of the global gravitational-wave detector network.}, number={6}, journal={Progress of Theoretical and Experimental Physics}, publisher={Oxford University Press (OUP)}, author={Abbott, R and Abe, H and Acernese, F and Ackley, K and Adhikari, N and Adhikari, R X and Adkins, V K and Adya, V B and Affeldt, C and Agarwal, D and et al.}, year={2022}, month={Apr} }
 @article{gretarsson_gretarsson_cole_harry_kinley-hanlon_jones_penn_2022, title={Measured limits on amplitude dependence of mechanical loss in substrate-transferred 
<mml:mrow><mml:mi>Ga
 coatings}, volume={106}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/physrevd.106.042001}, DOI={10.1103/PhysRevD.106.042001}, abstractNote={The standard approach for predicting thermal noise in optical mirrors using the fluctuation-dissipation theorem requires knowledge of the level of all significant sources of mechanical loss occurring at the oscillation amplitudes of thermal noise. Using a gentle nodal suspension system read out by a Michelson interferometer, we tested the amplitude-dependence of loss in $\mathrm{GaAs}/{\mathrm{Al}}_{0.92}{\mathrm{Ga}}_{0.08}\mathrm{As}$ multilayer optical coatings on silica substrates in the range from just above the rms thermal noise amplitude up to amplitudes typical of ringdown measurements: ${10}^{\ensuremath{-}1}--{10}^{3}$ picometers. None of the three samples tested showed any significant amplitude dependence over this range.}, number={4}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Gretarsson, Elizabeth M. and Gretarsson, Andri M. and Cole, Garrett D. and Harry, Gregory M. and Kinley-Hanlon, Maya M. and Jones, R. Jason and Penn, Steven D.}, year={2022}, month={Aug} }
 @article{abbott_abe_acernese_ackley_adhicary_adhikari_adhikari_adkins_adya_affeldt_et al._2022, title={Model-based Cross-correlation Search for Gravitational Waves from the Low-mass X-Ray Binary Scorpius X-1 in LIGO O3 Data}, volume={941}, ISSN={2041-8205 2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/aca1b0}, DOI={10.3847/2041-8213/aca1b0}, abstractNote={Abstract We present the results of a model-based search for continuous gravitational waves from the low-mass X-ray binary Scorpius X-1 using LIGO detector data from the third observing run of Advanced LIGO and Advanced Virgo. This is a semicoherent search that uses details of the signal model to coherently combine data separated by less than a specified coherence time, which can be adjusted to balance sensitivity with computing cost. The search covered a range of gravitational-wave frequencies from 25 to 1600 Hz, as well as ranges in orbital speed, frequency, and phase determined from observational constraints. No significant detection candidates were found, and upper limits were set as a function of frequency. The most stringent limits, between 100 and 200 Hz, correspond to an amplitude h 0 of about 10 −25 when marginalized isotropically over the unknown inclination angle of the neutron star’s rotation axis, or less than 4 × 10 −26 assuming the optimal orientation. The sensitivity of this search is now probing amplitudes predicted by models of torque balance equilibrium. For the usual conservative model assuming accretion at the surface of the neutron star, our isotropically marginalized upper limits are close to the predicted amplitude from about 70 to 100 Hz; the limits assuming that the neutron star spin is aligned with the most likely orbital angular momentum are below the conservative torque balance predictions from 40 to 200 Hz. Assuming a broader range of accretion models, our direct limits on gravitational-wave amplitude delve into the relevant parameter space over a wide range of frequencies, to 500 Hz or more.}, number={2}, journal={The Astrophysical Journal Letters}, publisher={American Astronomical Society}, author={Abbott, R. and Abe, H. and Acernese, F. and Ackley, K. and Adhicary, S. and Adhikari, N. and Adhikari, R. X. and Adkins, V. K. and Adya, V. B. and Affeldt, C. and et al.}, year={2022}, month={Dec}, pages={L30} }
 @article{abbott_abbott_acernese_ackley_adams_adhikari_adhikari_adya_affeldt_agarwal_et al._2022, title={Narrowband Searches for Continuous and Long-duration Transient Gravitational Waves from Known Pulsars in the LIGO-Virgo Third Observing Run}, volume={932}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/ac6ad0}, DOI={10.3847/1538-4357/ac6ad0}, abstractNote={Isolated neutron stars that are asymmetric with respect to their spin axis are possible sources of detectable continuous gravitational waves. This paper presents a fully-coherent search for such signals from eighteen pulsars in data from LIGO and Virgo's third observing run (O3). For known pulsars, efficient and sensitive matched-filter searches can be carried out if one assumes the gravitational radiation is phase-locked to the electromagnetic emission. In the search presented here, we relax this assumption and allow the frequency and frequency time-derivative of the gravitational waves to vary in a small range around those inferred from electromagnetic observations. We find no evidence for continuous gravitational waves, and set upper limits on the strain amplitude for each target. These limits are more constraining for seven of the targets than the spin-down limit defined by ascribing all rotational energy loss to gravitational radiation. In an additional search we look in O3 data for long-duration (hours-months) transient gravitational waves in the aftermath of pulsar glitches for six targets with a total of nine glitches. We report two marginal outliers from this search, but find no clear evidence for such emission either. The resulting duration-dependent strain upper limits do not surpass indirect energy constraints for any of these targets.}, number={2}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, N. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and Agarwal, D. and et al.}, year={2022}, month={Jun}, pages={133} }
 @article{kiessling_murray_kinley-hanlon_buchovska_ervik_graham_hough_johnston_pietsch_rowan_et al._2022, title={Quasi-monocrystalline silicon for low-noise end mirrors in cryogenic gravitational-wave detectors}, volume={4}, ISSN={2643-1564}, url={http://dx.doi.org/10.1103/physrevresearch.4.043043}, DOI={10.1103/PhysRevResearch.4.043043}, abstractNote={Mirrors made of silicon have been proposed for use in future cryogenic gravitational-wave detectors, which will be significantly more sensitive than current room-temperature detectors. These mirrors are planned to have diameters of $\ensuremath{\approx}50$ cm and a mass of $\ensuremath{\approx}200$ kg. While single-crystalline float-zone silicon meets the requirements of low optical absorption and low mechanical loss, the production of this type of material is restricted to sizes much smaller than required. Here we present studies of silicon produced by directional solidification. This material can be grown as quasi-monocrystalline ingots in sizes larger than currently required. We present measurements of a low room-temperature and cryogenic mechanical loss comparable with float-zone silicon. While the optical absorption of our test sample is significantly higher than required, the low mechanical loss motivates research into further absorption reduction in the future. While it is unclear if material pure enough for the transmissive detector input mirrors can be achieved, an absorption level suitable for the highly reflective coated end mirrors seems realistic. Together with the potential to produce samples much larger than $\ensuremath{\approx}50$ cm, this material may be of great benefit for realizing silicon-based gravitational-wave detectors.}, number={4}, journal={Physical Review Research}, publisher={American Physical Society (APS)}, author={Kiessling, Frank M. and Murray, Peter G. and Kinley-Hanlon, Maya and Buchovska, Iryna and Ervik, Torunn K. and Graham, Victoria and Hough, Jim and Johnston, Ross and Pietsch, Mike and Rowan, Sheila and et al.}, year={2022}, month={Oct} }
 @article{abbott_abbott_acernese_ackley_adams_adhikari_adhikari_adya_affeldt_agarwal_et al._2022, title={Search for Gravitational Waves Associated with Gamma-Ray Bursts Detected by Fermi and Swift during the LIGO–Virgo Run O3b}, volume={928}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/ac532b}, DOI={10.3847/1538-4357/ac532b}, abstractNote={We search for gravitational-wave signals associated with gamma-ray bursts detected by the Fermi and Swift satellites during the second half of the third observing run of Advanced LIGO and Advanced Virgo (1 November 2019 15:00 UTC-27 March 2020 17:00 UTC).We conduct two independent searches: a generic gravitational-wave transients search to analyze 86 gamma-ray bursts and an analysis to target binary mergers with at least one neutron star as short gamma-ray burst progenitors for 17 events. We find no significant evidence for gravitational-wave signals associated with any of these gamma-ray bursts. A weighted binomial test of the combined results finds no evidence for sub-threshold gravitational wave signals associated with this GRB ensemble either. We use several source types and signal morphologies during the searches, resulting in lower bounds on the estimated distance to each gamma-ray burst. Finally, we constrain the population of low luminosity short gamma-ray bursts using results from the first to the third observing runs of Advanced LIGO and Advanced Virgo. The resulting population is in accordance with the local binary neutron star merger rate.}, number={2}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, N. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and Agarwal, D. and et al.}, year={2022}, month={Apr}, pages={186} }
 @article{abbott_abbott_acernese_ackley_adams_adhikari_adhikari_adya_affeldt_agarwal_et al._2022, title={Search for Subsolar-Mass Binaries in the First Half of Advanced LIGO’s and Advanced Virgo’s Third Observing Run}, volume={129}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/PhysRevLett.129.061104}, DOI={10.1103/PhysRevLett.129.061104}, abstractNote={We report on a search for compact binary coalescences where at least one binary component has a mass between 0.2 $M_\odot$ and 1.0 $M_\odot$ in Advanced LIGO and Advanced Virgo data collected between 1 April 2019 1500 UTC and 1 October 2019 1500 UTC. We extend previous analyses in two main ways: we include data from the Virgo detector and we allow for more unequal mass systems, with mass ratio $q \geq 0.1$. We do not report any gravitational-wave candidates. The most significant trigger has a false alarm rate of 0.14 $\mathrm{yr}^{-1}$. This implies an upper limit on the merger rate of subsolar binaries in the range $[220-24200] \mathrm{Gpc}^{-3} \mathrm{yr}^{-1}$, depending on the chirp mass of the binary. We use this upper limit to derive astrophysical constraints on two phenomenological models that could produce subsolar-mass compact objects. One is an isotropic distribution of equal-mass primordial black holes. Using this model, we find that the fraction of dark matter in primordial black holes is $f_\mathrm{PBH} \equiv \Omega_\mathrm{PBH} / \Omega_\mathrm{DM} \lesssim 6\%$. The other is a dissipative dark matter model, in which fermionic dark matter can collapse and form black holes. The upper limit on the fraction of dark matter black holes depends on the minimum mass of the black holes that can be formed: the most constraining result is obtained at $M_\mathrm{min}=1 M_\odot$, where $f_\mathrm{DBH} \equiv \Omega_\mathrm{PBH} / \Omega_\mathrm{DM} \lesssim 0.003\%$. These are the tightest limits on spinning subsolar-mass binaries to date.}, number={6}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, N. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and Agarwal, D. and et al.}, year={2022}, month={Aug} }
 @article{abbott_abe_acernese_ackley_adhikari_adhikari_adkins_adya_affeldt_agarwal_et al._2022, title={Search for continuous gravitational wave emission from the Milky Way center in O3 LIGO-Virgo data}, volume={106}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.106.042003}, DOI={10.1103/PhysRevD.106.042003}, abstractNote={We present a directed search for continuous gravitational wave (CW) signals emitted by spinning neutron stars located in the inner parsecs of the Galactic Center (GC). Compelling evidence for the presence of a numerous population of neutron stars has been reported in the literature, turning this region into a very interesting place to look for CWs. In this search, data from the full O3 LIGO--Virgo run in the detector frequency band $[10,2000]\rm~Hz$ have been used. No significant detection was found and 95$\%$ confidence level upper limits on the signal strain amplitude were computed, over the full search band, with the deepest limit of about $7.6\times 10^{-26}$ at $\simeq 142\rm~Hz$. These results are significantly more constraining than those reported in previous searches. We use these limits to put constraints on the fiducial neutron star ellipticity and r-mode amplitude. These limits can be also translated into constraints in the black hole mass -- boson mass plane for a hypothetical population of boson clouds around spinning black holes located in the GC.}, number={4}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abe, H. and Acernese, F. and Ackley, K. and Adhikari, N. and Adhikari, R. X. and Adkins, V. K. and Adya, V. B. and Affeldt, C. and Agarwal, D. and et al.}, year={2022}, month={Aug} }
 @article{abbott_abbott_acernese_ackley_adams_adhikari_adhikari_adya_affeldt_agarwal_et al._2022, title={Search for continuous gravitational waves from 20 accreting millisecond x-ray pulsars in O3 LIGO data}, volume={105}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.105.022002}, DOI={10.1103/PhysRevD.105.022002}, abstractNote={Results are presented of searches for continuous gravitational waves from 20 accreting millisecond x-ray pulsars with accurately measured spin frequencies and orbital parameters, using data from the third observing run of the Advanced LIGO and Advanced Virgo detectors. The search algorithm uses a hidden Markov model, where the transition probabilities allow the frequency to wander according to an unbiased random walk, while the J-statistic maximum-likelihood matched filter tracks the binary orbital phase. Three narrow subbands are searched for each target, centered on harmonics of the measured spin frequency. The search yields 16 candidates, consistent with a false alarm probability of 30% per subband and target searched. These candidates, along with one candidate from an additional target-of-opportunity search done for SAX J1808.4−3658, which was in outburst during one month of the observing run, cannot be confidently associated with a known noise source. Additional follow-up does not provide convincing evidence that any are a true astrophysical signal. When all candidates are assumed nonastrophysical, upper limits are set on the maximum wave strain detectable at 95% confidence, h95%0. The strictest constraint is h95%0=4.7×10−26 from IGR J17062−6143. Constraints on the detectable wave strain from each target lead to constraints on neutron star ellipticity and r-mode amplitude, the strictest of which are ε95%=3.1×10−7 and α95%=1.8×10−5 respectively. This analysis is the most comprehensive and sensitive search of continuous gravitational waves from accreting millisecond x-ray pulsars to date.Received 19 September 2021Accepted 16 December 2021DOI:https://doi.org/10.1103/PhysRevD.105.022002© 2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasGravitational wavesPhysical SystemsBinary starsNeutron stars & pulsarsGravitation, Cosmology & Astrophysics}, number={2}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, N. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and Agarwal, D. and et al.}, year={2022}, month={Jan} }
 @article{abbott_abe_acernese_ackley_adhikari_adhikari_adkins_adya_affeldt_agarwal_et al._2022, title={Search for gravitational waves from Scorpius X-1 with a hidden Markov model in O3 LIGO data}, volume={106}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.106.062002}, DOI={10.1103/PhysRevD.106.062002}, abstractNote={Results are presented for a semi-coherent search for continuous gravitational waves from the low-mass X-ray binary Scorpius X-1, using a hidden Markov model (HMM) to allow for spin wandering. This search improves on previous HMM-based searches of Laser Interferometer Gravitational-wave Observatory (LIGO) data by including the orbital period in the search template grid, and by analyzing data from the latest (third) observing run (O3). In the frequency range searched, from 60 to 500 Hz, we find no evidence of gravitational radiation. This is the most sensitive search for Scorpius X-1 using a HMM to date. For the most sensitive sub-band, starting at $256.06$Hz, we report an upper limit on gravitational wave strain (at $95 \%$ confidence) of $h_{0}^{95\%}=6.16\times10^{-26}$, assuming the orbital inclination angle takes its electromagnetically restricted value $\iota=44^{\circ}$. The upper limits on gravitational wave strain reported here are on average a factor of $\sim 3$ lower than in the O2 HMM search. This is the first Scorpius X-1 HMM search with upper limits that reach below the indirect torque-balance limit for certain sub-bands, assuming $\iota=44^{\circ}$.}, number={6}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abe, H. and Acernese, F. and Ackley, K. and Adhikari, N. and Adhikari, R. X. and Adkins, V. K. and Adya, V. B. and Affeldt, C. and Agarwal, D. and et al.}, year={2022}, month={Sep} }
 @article{abbott_abbott_acernese_ackley_adams_adhikari_adhikari_adya_affeldt_agarwal_et al._2022, title={Search of the early O3 LIGO data for continuous gravitational waves from the Cassiopeia A and Vela Jr. supernova remnants}, volume={105}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.105.082005}, DOI={10.1103/PhysRevD.105.082005}, abstractNote={We present directed searches for continuous gravitational waves from the neutron stars in the Cassiopeia A (Cas A) and Vela Jr. supernova remnants. We carry out the searches in the LIGO data from the first six months of the third Advanced LIGO and Virgo observing run, using the Weave semi-coherent method, which sums matched-filter detection-statistic values over many time segments spanning the observation period. No gravitational wave signal is detected in the search band of 20--976 Hz for assumed source ages greater than 300 years for Cas A and greater than 700 years for Vela Jr. Estimates from simulated continuous wave signals indicate we achieve the most sensitive results to date across the explored parameter space volume, probing to strain magnitudes as low as ~$6.3\times10^{-26}$ for Cas A and ~$5.6\times10^{-26}$ for Vela Jr. at frequencies near 166 Hz at 95% efficiency.}, number={8}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, N. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and Agarwal, D. and et al.}, year={2022}, month={Apr} }
 @article{abbott_abe_acernese_ackley_adhikari_adhikari_adkins_adya_affeldt_agarwal_et al._2022, title={Searches for Gravitational Waves from Known Pulsars at Two Harmonics in the Second and Third LIGO-Virgo Observing Runs}, volume={935}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/ac6acf}, DOI={10.3847/1538-4357/ac6acf}, abstractNote={We present a targeted search for continuous gravitational waves (GWs) from 236 pulsars using data from the third observing run of LIGO and Virgo (O3) combined with data from the second observing run (O2). Searches were for emission from the $l=m=2$ mass quadrupole mode with a frequency at only twice the pulsar rotation frequency (single harmonic) and the $l=2, m=1,2$ modes with a frequency of both once and twice the rotation frequency (dual harmonic). No evidence of GWs was found so we present 95\% credible upper limits on the strain amplitudes $h_0$ for the single harmonic search along with limits on the pulsars' mass quadrupole moments $Q_{22}$ and ellipticities $\varepsilon$. Of the pulsars studied, 23 have strain amplitudes that are lower than the limits calculated from their electromagnetically measured spin-down rates. These pulsars include the millisecond pulsars J0437\textminus4715 and J0711\textminus6830 which have spin-down ratios of 0.87 and 0.57 respectively. For nine pulsars, their spin-down limits have been surpassed for the first time. For the Crab and Vela pulsars our limits are factors of $\sim 100$ and $\sim 20$ more constraining than their spin-down limits, respectively. For the dual harmonic searches, new limits are placed on the strain amplitudes $C_{21}$ and $C_{22}$. For 23 pulsars we also present limits on the emission amplitude assuming dipole radiation as predicted by Brans-Dicke theory.}, number={1}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Abbott, R. and Abe, H. and Acernese, F. and Ackley, K. and Adhikari, N. and Adhikari, R. X. and Adkins, V. K. and Adya, V. B. and Affeldt, C. and Agarwal, D. and et al.}, year={2022}, month={Aug}, pages={1} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2021, title={A Gravitational-wave Measurement of the Hubble Constant Following the Second Observing Run of Advanced LIGO and Virgo}, volume={909}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/abdcb7}, DOI={10.3847/1538-4357/abdcb7}, abstractNote={This paper presents the gravitational-wave measurement of the Hubble constant ($H_0$) using the detections from the first and second observing runs of the Advanced LIGO and Virgo detector network. The presence of the transient electromagnetic counterpart of the binary neutron star GW170817 led to the first standard-siren measurement of $H_0$. Here we additionally use binary black hole detections in conjunction with galaxy catalogs and report a joint measurement. Our updated measurement is $H_0 = 68.7^{+17.0}_{-7.8}$ km/s/Mpc (68.3\% of the highest density posterior interval with a flat-in-log prior) which is an improvement by a factor of 1.04 (about 4\%) over the GW170817-only value of $68.7^{+17.5}_{-8.3}$ km/s/Mpc. A significant additional contribution currently comes from GW170814, a loud and well-localized detection from a part of the sky thoroughly covered by the Dark Energy Survey. With numerous detections anticipated over the upcoming years, an exhaustive understanding of other systematic effects are also going to become increasingly important. These results establish the path to cosmology using gravitational-wave observations with and without transient electromagnetic counterparts.}, number={2}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2021}, month={Mar}, pages={218} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adams_adhikari_adya_affeldt_et al._2021, title={All-sky search for continuous gravitational waves from isolated neutron stars in the early O3 LIGO data}, volume={104}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.104.082004}, DOI={10.1103/PhysRevD.104.082004}, abstractNote={We report on an all-sky search for continuous gravitational waves in the frequency band 20–2000 Hz and with a frequency time derivative in the range of [−1.0,+0.1]×10−8 Hz/s. Such a signal could be produced by a nearby, spinning and slightly nonaxisymmetric isolated neutron star in our Galaxy. This search uses the LIGO data from the first six months of Advanced LIGO’s and Advanced Virgo’s third observational run, O3. No periodic gravitational wave signals are observed, and 95% confidence-level (C.L.) frequentist upper limits are placed on their strengths. The lowest upper limits on worst-case (linearly polarized) strain amplitude h0 are ∼1.7×10−25 near 200 Hz. For a circularly polarized source (most favorable orientation), the lowest upper limits are ∼6.3×10−26. These strict frequentist upper limits refer to all sky locations and the entire range of frequency derivative values. For a population-averaged ensemble of sky locations and stellar orientations, the lowest 95% C.L. upper limits on the strain amplitude are ∼1.4×10−25. These upper limits improve upon our previously published all-sky results, with the greatest improvement (factor of ∼2) seen at higher frequencies, in part because quantum squeezing has dramatically improved the detector noise level relative to the second observational run, O2. These limits are the most constraining to date over most of the parameter space searched.Received 1 July 2021Accepted 16 September 2021DOI:https://doi.org/10.1103/PhysRevD.104.082004© 2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAstrophysical studies of gravityGravitational wave detectionGravitational wave sourcesGravitational wavesGravitation, Cosmology & Astrophysics}, number={8}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, A. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2021}, month={Oct} }
 @article{abbott_abbott_acernese_ackley_adams_adhikari_adhikari_adya_affeldt_agarwal_et al._2021, title={All-sky search for long-duration gravitational-wave bursts in the third Advanced LIGO and Advanced Virgo run}, volume={104}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.104.102001}, DOI={10.1103/PhysRevD.104.102001}, abstractNote={After the detection of gravitational waves from compact binary coalescences, the search for transient gravitational-wave signals with less well-defined waveforms for which matched filtering is not well suited is one of the frontiers for gravitational-wave astronomy. Broadly classified into ``short'' $\ensuremath{\lesssim}1\text{ }\text{ }\mathrm{s}$ and ``long'' $\ensuremath{\gtrsim}1\text{ }\text{ }\mathrm{s}$ duration signals, these signals are expected from a variety of astrophysical processes, including non-axisymmetric deformations in magnetars or eccentric binary black hole coalescences. In this work, we present a search for long-duration gravitational-wave transients from Advanced LIGO and Advanced Virgo's third observing run from April 2019 to March 2020. For this search, we use minimal assumptions for the sky location, event time, waveform morphology, and duration of the source. The search covers the range of 2--500 s in duration and a frequency band of 24--2048 Hz. We find no significant triggers within this parameter space; we report sensitivity limits on the signal strength of gravitational waves characterized by the root-sum-square amplitude ${h}_{\mathrm{rss}}$ as a function of waveform morphology. These ${h}_{\mathrm{rss}}$ limits improve upon the results from the second observing run by an average factor of 1.8.}, number={10}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, N. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and Agarwal, D. and et al.}, year={2021}, month={Nov} }
 @article{abbott_abbott_acernese_ackley_adams_adhikari_adhikari_adya_affeldt_agarwal_et al._2021, title={All-sky search for short gravitational-wave bursts in the third Advanced LIGO and Advanced Virgo run}, volume={104}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.104.122004}, DOI={10.1103/PhysRevD.104.122004}, abstractNote={This paper presents the results of a search for generic short-duration gravitational-wave transients in data from the third observing run of Advanced LIGO and Advanced Virgo. Transients with durations of milliseconds to a few seconds in the 24--4096 Hz frequency band are targeted by the search, with no assumptions made regarding the incoming signal direction, polarization, or morphology. Gravitational waves from compact binary coalescences that have been identified by other targeted analyses are detected, but no statistically significant evidence for other gravitational wave bursts is found. Sensitivities to a variety of signals are presented. These include updated upper limits on the source rate density as a function of the characteristic frequency of the signal, which are roughly an order of magnitude better than previous upper limits. This search is sensitive to sources radiating as little as $\ensuremath{\sim}{10}^{\ensuremath{-}10}\text{ }\text{ }{M}_{\ensuremath{\bigodot}}{c}^{2}$ in gravitational waves at $\ensuremath{\sim}70\text{ }\text{ }\mathrm{Hz}$ from a distance of 10 kpc, with 50% detection efficiency at a false alarm rate of one per century. The sensitivity of this search to two plausible astrophysical sources is estimated: neutron star $f$ modes, which may be excited by pulsar glitches, as well as selected core-collapse supernova models.}, number={12}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, N. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and Agarwal, D. and et al.}, year={2021}, month={Dec} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adams_adhikari_adya_affeldt_et al._2021, title={All-sky search in early O3 LIGO data for continuous gravitational-wave signals from unknown neutron stars in binary systems}, volume={103}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.103.064017}, DOI={10.1103/PhysRevD.103.064017}, abstractNote={Rapidly spinning neutron stars are promising sources of continuous gravitational waves. Detecting such a signal would allow probing of the physical properties of matter under extreme conditions. A significant fraction of the known pulsar population belongs to binary systems. Searching for unknown neutron stars in binary systems requires specialized algorithms to address unknown orbital frequency modulations. We present a search for continuous gravitational waves emitted by neutron stars in binary systems in early data from the third observing run of the Advanced LIGO and Advanced Virgo detectors using the semicoherent, GPU-accelerated, binaryskyhough pipeline. The search analyzes the most sensitive frequency band of the LIGO detectors, 50–300 Hz. Binary orbital parameters are split into four regions, comprising orbital periods of three to 45 days and projected semimajor axes of two to 40 light seconds. No detections are reported. We estimate the sensitivity of the search using simulated continuous wave signals, achieving the most sensitive results to date across the analyzed parameter space.5 MoreReceived 23 December 2020Accepted 3 February 2021DOI:https://doi.org/10.1103/PhysRevD.103.064017© 2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasGravitational wave detectionGravitational wave sourcesGravitational wavesPhysical SystemsBinary starsNeutron stars & pulsarsGravitation, Cosmology & Astrophysics}, number={6}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, A. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2021}, month={Mar} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adams_adhikari_adya_affeldt_et al._2021, title={Constraints from LIGO O3 Data on Gravitational-wave Emission Due to R-modes in the Glitching Pulsar PSR J0537–6910}, volume={922}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/ac0d52}, DOI={10.3847/1538-4357/ac0d52}, abstractNote={Abstract We present a search for continuous gravitational-wave emission due to r-modes in the pulsar PSR J0537–6910 using data from the LIGO–Virgo Collaboration observing run O3. PSR J0537–6910 is a young energetic X-ray pulsar and is the most frequent glitcher known. The inter-glitch braking index of the pulsar suggests that gravitational-wave emission due to r-mode oscillations may play an important role in the spin evolution of this pulsar. Theoretical models confirm this possibility and predict emission at a level that can be probed by ground-based detectors. In order to explore this scenario, we search for r-mode emission in the epochs between glitches by using a contemporaneous timing ephemeris obtained from NICER data. We do not detect any signals in the theoretically expected band of 86–97 Hz, and report upper limits on the amplitude of the gravitational waves. Our results improve on previous amplitude upper limits from r-modes in J0537-6910 by a factor of up to 3 and place stringent constraints on theoretical models for r-mode-driven spin-down in PSR J0537–6910, especially for higher frequencies at which our results reach below the spin-down limit defined by energy conservation.}, number={1}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, A. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2021}, month={Nov}, pages={71} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adams_adhikari_adya_affeldt_et al._2021, title={Constraints on Cosmic Strings Using Data from the Third Advanced LIGO–Virgo Observing Run}, volume={126}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/PhysRevLett.126.241102}, DOI={10.1103/PhysRevLett.126.241102}, abstractNote={A search for gravitational-wave signals produced by cosmic strings in the Advanced LIGO and Virgo full O3 data set improve upon the previous LIGO-Virgo constraints on G\ensuremath{\mu} by one to two orders of magnitude, depending on the model which is tested.}, number={24}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, A. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2021}, month={Jun} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adams_adhikari_adya_affeldt_et al._2021, title={Diving below the Spin-down Limit: Constraints on Gravitational Waves from the Energetic Young Pulsar PSR J0537-6910}, volume={913}, ISSN={2041-8205 2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/abffcd}, DOI={10.3847/2041-8213/abffcd}, abstractNote={Abstract We present a search for quasi-monochromatic gravitational-wave signals from the young, energetic X-ray pulsar PSR J0537−6910 using data from the second and third observing runs of LIGO and Virgo. The search is enabled by a contemporaneous timing ephemeris obtained using Neutron star Interior Composition Explorer (NICER) data. The NICER ephemeris has also been extended through 2020 October and includes three new glitches. PSR J0537−6910 has the largest spin-down luminosity of any pulsar and exhibits fRequent and strong glitches. Analyses of its long-term and interglitch braking indices provide intriguing evidence that its spin-down energy budget may include gravitational-wave emission from a time-varying mass quadrupole moment. Its 62 Hz rotation frequency also puts its possible gravitational-wave emission in the most sensitive band of the LIGO/Virgo detectors. Motivated by these considerations, we search for gravitational-wave emission at both once and twice the rotation frequency from PSR J0537−6910. We find no signal, however, and report upper limits. Assuming a rigidly rotating triaxial star, our constraints reach below the gravitational-wave spin-down limit for this star for the first time by more than a factor of 2 and limit gravitational waves from the l = m = 2 mode to account for less than 14% of the spin-down energy budget. The fiducial equatorial ellipticity is constrained to less than about 3 ×10 −5 , which is the third best constraint for any young pulsar.}, number={2}, journal={The Astrophysical Journal Letters}, publisher={American Astronomical Society}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, A. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2021}, month={May}, pages={L27} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adams_adhikari_adya_affeldt_et al._2021, title={GWTC-2: Compact Binary Coalescences Observed by LIGO and Virgo during the First Half of the Third Observing Run}, volume={11}, ISSN={2160-3308}, url={http://dx.doi.org/10.1103/PhysRevX.11.021053}, DOI={10.1103/PhysRevX.11.021053}, abstractNote={We report on gravitational-wave discoveries from compact binary coalescences detected by Advanced LIGO and Advanced Virgo in the first half of the third observing run (O3a) between 1 April 2019 15∶00 UTC and 1 October 2019 15∶00 UTC. By imposing a false-alarm-rate threshold of two per year in each of the four search pipelines that constitute our search, we present 39 candidate gravitational-wave events. At this threshold, we expect a contamination fraction of less than 10%. Of these, 26 candidate events were reported previously in near-real time through gamma-ray coordinates network notices and circulars; 13 are reported here for the first time. The catalog contains events whose sources are black hole binary mergers up to a redshift of approximately 0.8, as well as events whose components cannot be unambiguously identified as black holes or neutron stars. For the latter group, we are unable to determine the nature based on estimates of the component masses and spins from gravitational-wave data alone. The range of candidate event masses which are unambiguously identified as binary black holes (both objects ≥3 M⊙) is increased compared to GWTC-1, with total masses from approximately 14 M⊙ for GW190924_021846 to approximately 150 M⊙ for GW190521. For the first time, this catalog includes binary systems with significantly asymmetric mass ratios, which had not been observed in data taken before April 2019. We also find that 11 of the 39 events detected since April 2019 have positive effective inspiral spins under our default prior (at 90% credibility), while none exhibit negative effective inspiral spin. Given the increased sensitivity of Advanced LIGO and Advanced Virgo, the detection of 39 candidate events in approximately 26 weeks of data (approximately 1.5 per week) is consistent with GWTC-1.10 MoreReceived 30 October 2020Revised 23 February 2021Accepted 20 April 2021Corrected 27 April 2022Corrected 1 September 2021DOI:https://doi.org/10.1103/PhysRevX.11.021053Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasGravitational wave detectionGravitational wave sourcesGravitation, Cosmology & Astrophysics}, number={2}, journal={Physical Review X}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, A. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2021}, month={Jun} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adams_adhikari_adya_affeldt_et al._2021, title={Observation of Gravitational Waves from Two Neutron Star–Black Hole Coalescences}, volume={915}, ISSN={2041-8205 2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/ac082e}, DOI={10.3847/2041-8213/ac082e}, abstractNote={We report the observation of gravitational waves from two compact binary coalescences in LIGO's and Virgo's third observing run with properties consistent with neutron star-black hole (NSBH) binaries. The two events are named GW200105_162426 and GW200115_042309, abbreviated as GW200105 and GW200115; the first was observed by LIGO Livingston and Virgo, and the second by all three LIGO-Virgo detectors. The source of GW200105 has component masses $8.9^{+1.2}_{-1.5}\,M_\odot$ and $1.9^{+0.3}_{-0.2}\,M_\odot$, whereas the source of GW200115 has component masses $5.7^{+1.8}_{-2.1}\,M_\odot$ and $1.5^{+0.7}_{-0.3}\,M_\odot$ (all measurements quoted at the 90% credible level). The probability that the secondary's mass is below the maximal mass of a neutron star is 89%-96% and 87%-98%, respectively, for GW200105 and GW200115, with the ranges arising from different astrophysical assumptions. The source luminosity distances are $280^{+110}_{-110}$ Mpc and $300^{+150}_{-100}$ Mpc, respectively. The magnitude of the primary spin of GW200105 is less than 0.23 at the 90% credible level, and its orientation is unconstrained. For GW200115, the primary spin has a negative spin projection onto the orbital angular momentum at 88% probability. We are unable to constrain spin or tidal deformation of the secondary component for either event. We infer a NSBH merger rate density of $45^{+75}_{-33}\,\mathrm{Gpc}^{-3} \mathrm{yr}^{-1}$ when assuming GW200105 and GW200115 are representative of the NSBH population, or $130^{+112}_{-69}\,\mathrm{Gpc}^{-3} \mathrm{yr}^{-1}$ under the assumption of a broader distribution of component masses.}, number={1}, journal={The Astrophysical Journal Letters}, publisher={American Astronomical Society}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, A. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2021}, month={Jun}, pages={L5} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adams_adhikari_adya_affeldt_et al._2021, title={Population Properties of Compact Objects from the Second LIGO–Virgo Gravitational-Wave Transient Catalog}, volume={913}, ISSN={2041-8205 2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/abe949}, DOI={10.3847/2041-8213/abe949}, abstractNote={Abstract We report on the population of 47 compact binary mergers detected with a false-alarm rate of < <?CDATA $1\,{\mathrm{yr}}^{-1}$?> in the second LIGO–Virgo Gravitational-Wave Transient Catalog. We observe several characteristics of the merging binary black hole (BBH) population not discernible until now. First, the primary mass spectrum contains structure beyond a power law with a sharp high-mass cutoff; it is more consistent with a broken power law with a break at <?CDATA ${39.7}_{-9.1}^{+20.3}\,\,{M}_{\odot }$?> or a power law with a Gaussian feature peaking at <?CDATA ${33.1}_{-5.6}^{+4.0}\,\,{M}_{\odot }$?> (90% credible interval). While the primary mass distribution must extend to <?CDATA $\sim 65\,{M}_{\odot }$?> or beyond, only <?CDATA ${2.9}_{-1.7}^{+3.5} \% $?> of systems have primary masses greater than <?CDATA $45\,{M}_{\odot }$?> . Second, we find that a fraction of BBH systems have component spins misaligned with the orbital angular momentum, giving rise to precession of the orbital plane. Moreover, <?CDATA $12$?> %– <?CDATA $44$?> % of BBH systems have spins tilted by more than 90°, giving rise to a negative effective inspiral spin parameter, <?CDATA ${\chi }_{\mathrm{eff}}$?> . Under the assumption that such systems can only be formed by dynamical interactions, we infer that between 25% and 93% of BBHs with nonvanishing <?CDATA $| {\chi }_{\mathrm{eff}}| \gt 0.01$?> are dynamically assembled. Third, we estimate merger rates, finding <?CDATA ${{ \mathcal R }}_{\mathrm{BBH}}={23.9}_{-8.6}^{+14.3}\,\,{\mathrm{Gpc}}^{-3}\,{\mathrm{yr}}^{-1}$?> for BBHs and <?CDATA ${{ \mathcal R }}_{\mathrm{BNS}}={320}_{-240}^{+490}\,\,{\mathrm{Gpc}}^{-3}\,{\mathrm{yr}}^{-1}$?> for binary neutron stars. We find that the BBH rate likely increases with redshift ( <?CDATA $85 \% $?> credibility) but not faster than the star formation rate ( <?CDATA $86 \% $?> credibility). Additionally, we examine recent exceptional events in the context of our population models, finding that the asymmetric masses of GW190412 and the high component masses of GW190521 are consistent with our models, but the low secondary mass of GW190814 makes it an outlier.}, number={1}, journal={The Astrophysical Journal Letters}, publisher={American Astronomical Society}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, A. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2021}, month={May}, pages={L7} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_agathos_et al._2021, title={Search for Gravitational Waves Associated with Gamma-Ray Bursts Detected by Fermi and Swift during the LIGO–Virgo Run O3a}, volume={915}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/abee15}, DOI={10.3847/1538-4357/abee15}, abstractNote={We search for gravitational-wave transients associated with gamma-ray bursts detected by the Fermi and Swift satellites during the first part of the third observing run of Advanced LIGO and Advanced Virgo (1 April 2019 15:00 UTC - 1 October 2019 15:00 UTC). 105 gamma-ray bursts were analyzed using a search for generic gravitational-wave transients; 32 gamma-ray bursts were analyzed with a search that specifically targets neutron star binary mergers as short gamma-ray burst progenitors. We describe a method to calculate the probability that triggers from the binary merger targeted search are astrophysical and apply that method to the most significant gamma-ray bursts in that search. We find no significant evidence for gravitational-wave signals associated with the gamma-ray bursts that we followed up, nor for a population of unidentified subthreshold signals. We consider several source types and signal morphologies, and report for these lower bounds on the distance to each gamma-ray burst.}, number={2}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and Agathos, M. and et al.}, year={2021}, month={Jul}, pages={86} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adams_adhikari_adya_affeldt_et al._2021, title={Search for Lensing Signatures in the Gravitational-Wave Observations from the First Half of LIGO–Virgo’s Third Observing Run}, volume={923}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/ac23db}, DOI={10.3847/1538-4357/ac23db}, abstractNote={We search for signatures of gravitational lensing in the gravitational-wave signals from compact binary coalescences detected by Advanced LIGO and Advanced Virgo during O3a, the first half of their third observing run. We study: 1) the expected rate of lensing at current detector sensitivity and the implications of a non-observation of strong lensing or a stochastic gravitational-wave background on the merger-rate density at high redshift; 2) how the interpretation of individual high-mass events would change if they were found to be lensed; 3) the possibility of multiple images due to strong lensing by galaxies or galaxy clusters; and 4) possible wave-optics effects due to point-mass microlenses. Several pairs of signals in the multiple-image analysis show similar parameters and, in this sense, are nominally consistent with the strong lensing hypothesis. However, taking into account population priors, selection effects, and the prior odds against lensing, these events do not provide sufficient evidence for lensing. Overall, we find no compelling evidence for lensing in the observed gravitational-wave signals from any of these analyses.}, number={1}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, A. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2021}, month={Dec}, pages={14} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adams_adhikari_adya_affeldt_et al._2021, title={Search for anisotropic gravitational-wave backgrounds using data from Advanced LIGO and Advanced Virgo’s first three observing runs}, volume={104}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.104.022005}, DOI={10.1103/PhysRevD.104.022005}, abstractNote={We report results from searches for anisotropic stochastic gravitational-wave backgrounds using data from the first three observing runs of the Advanced LIGO and Advanced Virgo detectors. For the first time, we include Virgo data in our analysis and run our search with a new efficient pipeline called {\tt PyStoch} on data folded over one sidereal day. We use gravitational-wave radiometry (broadband and narrow band) to produce sky maps of stochastic gravitational-wave backgrounds and to search for gravitational waves from point sources. A spherical harmonic decomposition method is employed to look for gravitational-wave emission from spatially-extended sources. Neither technique found evidence of gravitational-wave signals. Hence we derive 95\% confidence-level upper limit sky maps on the gravitational-wave energy flux from broadband point sources, ranging from $F_{\alpha, \Theta} < {\rm (0.013 - 7.6)} \times 10^{-8} {\rm erg \, cm^{-2} \, s^{-1} \, Hz^{-1}},$ and on the (normalized) gravitational-wave energy density spectrum from extended sources, ranging from $\Omega_{\alpha, \Theta} < {\rm (0.57 - 9.3)} \times 10^{-9} \, {\rm sr^{-1}}$, depending on direction ($\Theta$) and spectral index ($\alpha$). These limits improve upon previous limits by factors of $2.9 - 3.5$. We also set 95\% confidence level upper limits on the frequency-dependent strain amplitudes of quasimonochromatic gravitational waves coming from three interesting targets, Scorpius X-1, SN 1987A and the Galactic Center, with best upper limits range from $h_0 < {\rm (1.7-2.1)} \times 10^{-25},$ a factor of $\geq 2.0$ improvement compared to previous stochastic radiometer searches.}, number={2}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, A. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2021}, month={Jul} }
 @article{abbott_abbott_acernese_ackley_adams_adhikari_adhikari_adya_affeldt_agarwal_et al._2022, title={Search for intermediate-mass black hole binaries in the third observing run of Advanced LIGO and Advanced Virgo}, volume={659}, ISSN={0004-6361 1432-0746}, url={http://dx.doi.org/10.1051/0004-6361/202141452}, DOI={10.1051/0004-6361/202141452}, abstractNote={Intermediate-mass black holes (IMBHs) span the approximate mass range $100$--$10^5\,M_\odot$, between black holes (BHs) formed by stellar collapse and the supermassive BHs at the centers of galaxies. Mergers of IMBH binaries are the most energetic gravitational-wave sources accessible by the terrestrial detector network. Searches of the first two observing runs of Advanced LIGO and Advanced Virgo did not yield any significant IMBH binary signals. In the third observing run (O3), the increased network sensitivity enabled the detection of GW190521, a signal consistent with a binary merger of mass $\sim 150\,M_\odot\,$ providing direct evidence of IMBH formation. Here we report on a dedicated search of O3 data for further IMBH binary mergers, combining both modelled (matched filter) and model independent search methods. We find some marginal candidates, but none are sufficiently significant to indicate detection of further IMBH mergers. We quantify the sensitivity of the individual search methods and of the combined search using a suite of IMBH binary signals obtained via numerical relativity, including the effects of spins misaligned with the binary orbital axis, and present the resulting upper limits on astrophysical merger rates. Our most stringent limit is for equal mass and aligned spin BH binary of total mass $200\,M_\odot$ and effective aligned spin 0.8 at $0.056\,Gpc^{-3} yr^{-1}$ (90 $\%$ confidence), a factor of 3.5 more constraining than previous LIGO-Virgo limits. We also update the estimated rate of mergers similar to GW190521 to $0.08\, Gpc^{-3}yr^{-1}$.}, journal={Astronomy & Astrophysics}, publisher={EDP Sciences}, author={Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, N. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and Agarwal, D. and et al.}, year={2022}, month={Mar}, pages={A84} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adams_adhikari_adya_affeldt_et al._2021, title={Searches for Continuous Gravitational Waves from Young Supernova Remnants in the Early Third Observing Run of Advanced LIGO and Virgo}, volume={921}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/ac17ea}, DOI={10.3847/1538-4357/ac17ea}, abstractNote={We present results of three wide-band directed searches for continuous gravitational waves from 15 young supernova remnants in the first half of the third Advanced LIGO and Virgo observing run. We use three search pipelines with distinct signal models and methods of identifying noise artifacts. Without ephemerides of these sources, the searches are conducted over a frequency band spanning from 10~Hz to 2~kHz. We find no evidence of continuous gravitational radiation from these sources. We set upper limits on the intrinsic signal strain at 95\% confidence level in sample sub-bands, estimate the sensitivity in the full band, and derive the corresponding constraints on the fiducial neutron star ellipticity and $r$-mode amplitude. The best 95\% confidence constraints placed on the signal strain are $7.7\times 10^{-26}$ and $7.8\times 10^{-26}$ near 200~Hz for the supernova remnants G39.2--0.3 and G65.7+1.2, respectively. The most stringent constraints on the ellipticity and $r$-mode amplitude reach $\lesssim 10^{-7}$ and $ \lesssim 10^{-5}$, respectively, at frequencies above $\sim 400$~Hz for the closest supernova remnant G266.2--1.2/Vela Jr.}, number={1}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, A. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2021}, month={Nov}, pages={80} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adams_adhikari_adya_affeldt_et al._2021, title={Tests of general relativity with binary black holes from the second LIGO-Virgo gravitational-wave transient catalog}, volume={103}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.103.122002}, DOI={10.1103/PhysRevD.103.122002}, abstractNote={Gravitational waves enable tests of general relativity in the highly dynamical and strong-field regime. Using events detected by LIGO-Virgo up to 1 October 2019, we evaluate the consistency of the data with predictions from the theory. We first establish that residuals from the best-fit waveform are consistent with detector noise, and that the low- and high-frequency parts of the signals are in agreement. We then consider parametrized modifications to the waveform by varying post-Newtonian and phenomenological coefficients, improving past constraints by factors of $\ensuremath{\sim}2$; we also find consistency with Kerr black holes when we specifically target signatures of the spin-induced quadrupole moment. Looking for gravitational-wave dispersion, we tighten constraints on Lorentz-violating coefficients by a factor of $\ensuremath{\sim}2.6$ and bound the mass of the graviton to ${m}_{g}\ensuremath{\le}1.76\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}23}\text{ }\text{ }\mathrm{eV}/{c}^{2}$ with 90% credibility. We also analyze the properties of the merger remnants by measuring ringdown frequencies and damping times, constraining fractional deviations away from the Kerr frequency to $\ensuremath{\delta}{\stackrel{^}{f}}_{220}=0.0{3}_{\ensuremath{-}0.35}^{+0.38}$ for the fundamental quadrupolar mode, and $\ensuremath{\delta}{\stackrel{^}{f}}_{221}=0.0{4}_{\ensuremath{-}0.32}^{+0.27}$ for the first overtone; additionally, we find no evidence for postmerger echoes. Finally, we determine that our data are consistent with tensorial polarizations through a template-independent method. When possible, we assess the validity of general relativity based on collections of events analyzed jointly. We find no evidence for new physics beyond general relativity, for black hole mimickers, or for any unaccounted systematics.}, number={12}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, A. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2021}, month={Jun} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adams_adhikari_adya_affeldt_et al._2021, title={Upper limits on the isotropic gravitational-wave background from Advanced LIGO and Advanced Virgo’s third observing run}, volume={104}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.104.022004}, DOI={10.1103/PhysRevD.104.022004}, abstractNote={We report results of a search for an isotropic gravitational-wave background (GWB) using data from Advanced LIGO's and Advanced Virgo's third observing run (O3) combined with upper limits from the earlier O1 and O2 runs. Unlike in previous observing runs in the advanced detector era, we include Virgo in the search for the GWB. The results are consistent with uncorrelated noise, and therefore we place upper limits on the strength of the GWB. We find that the dimensionless energy density $\Omega_{\rm GW}\leq 5.8\times 10^{-9}$ at the 95% credible level for a flat (frequency-independent) GWB, using a prior which is uniform in the log of the strength of the GWB, with 99% of the sensitivity coming from the band 20-76.6 Hz; $\leq 3.4 \times 10^{-9}$ at 25 Hz for a power-law GWB with a spectral index of 2/3 (consistent with expectations for compact binary coalescences), in the band 20-90.6 Hz; and $\leq 3.9 \times 10^{-10}$ at 25 Hz for a spectral index of 3, in the band 20-291.6 Hz. These upper limits improve over our previous results by a factor of 6.0 for a flat GWB. We also search for a GWB arising from scalar and vector modes, which are predicted by alternative theories of gravity; we place upper limits on the strength of GWBs with these polarizations. We demonstrate that there is no evidence of correlated noise of magnetic origin by performing a Bayesian analysis that allows for the presence of both a GWB and an effective magnetic background arising from geophysical Schumann resonances. We compare our upper limits to a fiducial model for the GWB from the merger of compact binaries. Finally, we combine our results with observations of individual mergers andshow that, at design sensitivity, this joint approach may yield stronger constraints on the merger rate of binary black holes at $z \lesssim 2$ than can be achieved with individually resolved mergers alone. [abridged]}, number={2}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, A. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2021}, month={Jul} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adya_affeldt_agathos_et al._2020, title={A guide to LIGO–Virgo detector noise and extraction of transient gravitational-wave signals}, volume={37}, ISSN={0264-9381 1361-6382}, url={http://dx.doi.org/10.1088/1361-6382/ab685e}, DOI={10.1088/1361-6382/ab685e}, abstractNote={Abstract The LIGO Scientific Collaboration and the Virgo Collaboration have cataloged eleven confidently detected gravitational-wave events during the first two observing runs of the advanced detector era. All eleven events were consistent with being from well-modeled mergers between compact stellar-mass objects: black holes or neutron stars. The data around the time of each of these events have been made publicly available through the gravitational-wave open science center. The entirety of the gravitational-wave strain data from the first and second observing runs have also now been made publicly available. There is considerable interest among the broad scientific community in understanding the data and methods used in the analyses. In this paper, we provide an overview of the detector noise properties and the data analysis techniques used to detect gravitational-wave signals and infer the source properties. We describe some of the checks that are performed to validate the analyses and results from the observations of gravitational-wave events. We also address concerns that have been raised about various properties of LIGO–Virgo detector noise and the correctness of our analyses as applied to the resulting data.}, number={5}, journal={Classical and Quantum Gravity}, publisher={IOP Publishing}, author={Abbott, B P and Abbott, R and Abbott, T D and Abraham, S and Acernese, F and Ackley, K and Adams, C and Adya, V B and Affeldt, C and Agathos, M and et al.}, year={2020}, month={Feb}, pages={055002} }
 @article{tait_steinlechner_kinley-hanlon_murray_hough_mcghee_pein_rowan_schnabel_smith_et al._2020, title={Demonstration of the Multimaterial Coating Concept to Reduce Thermal Noise in Gravitational-Wave Detectors}, volume={125}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/physrevlett.125.011102}, DOI={10.1103/PhysRevLett.125.011102}, abstractNote={Thermal noise associated with the mechanical loss of current highly reflective mirror coatings is a critical limit to the sensitivity of gravitational-wave detectors. Several alternative coating materials show potential for reducing thermal noise, but cannot be used due to their high optical absorption. Multimaterial coatings have been proposed to enable the use of such materials to reduce thermal noise while minimizing their impact on the total absorption of the mirror coating. Here we present experimental verification of the multimaterial concept, by integrating aSi into a highly reflective ${\mathrm{SiO}}_{2}$ and ${\mathrm{Ta}}_{2}{\mathrm{O}}_{5}$ multilayer coating. We show a significant thermal noise improvement and demonstrate consistent optical and mechanical performance. The multimaterial coating survives the heat treatment required to minimize the absorption of the aSi layers, with no adverse effects from the different thermomechanical properties of the three materials.}, number={1}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Tait, Simon C. and Steinlechner, Jessica and Kinley-Hanlon, Maya M. and Murray, Peter G. and Hough, Jim and McGhee, Graeme and Pein, Felix and Rowan, Sheila and Schnabel, Roman and Smith, Cassady and et al.}, year={2020}, month={Jul} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_agathos_et al._2020, title={GW190412: Observation of a binary-black-hole coalescence with asymmetric masses}, volume={102}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.102.043015}, DOI={10.1103/PhysRevD.102.043015}, abstractNote={We report the observation of gravitational waves from a binary-black-hole coalescence during the first two weeks of LIGO's and Virgo's third observing run. The signal was recorded on April 12, 2019 at 05:30:44 UTC with a network signal-to-noise ratio of 19. The binary is different from observations during the first two observing runs most notably due to its asymmetric masses: a ~30 solar mass black hole merged with a ~8 solar mass black hole companion. The more massive black hole rotated with a dimensionless spin magnitude between 0.22 and 0.60 (90% probability). Asymmetric systems are predicted to emit gravitational waves with stronger contributions from higher multipoles, and indeed we find strong evidence for gravitational radiation beyond the leading quadrupolar order in the observed signal. A suite of tests performed on GW190412 indicates consistency with Einstein's general theory of relativity. While the mass ratio of this system differs from all previous detections, we show that it is consistent with the population model of stellar binary black holes inferred from the first two observing runs.}, number={4}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and Agathos, M. and et al.}, year={2020}, month={Aug} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2020, title={GW190425: Observation of a Compact Binary Coalescence with Total Mass ∼ 3.4 M<sub>⊙}, volume={892}, ISSN={2041-8205 2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/ab75f5}, DOI={10.3847/2041-8213/ab75f5}, abstractNote={On 2019 April 25, the LIGO Livingston detector observed a compact binary coalescence with signal-to-noise ratio 12.9. The Virgo detector was also taking data that did not contribute to detection due to a low signal-to-noise ratio, but were used for subsequent parameter estimation. The 90% credible intervals for the component masses range from 1.12 to 2.52 $M_{\odot}$ (1.45 to 1.88 $M_{\odot}$ if we restrict the dimensionless component spin magnitudes to be smaller than 0.05). These mass parameters are consistent with the individual binary components being neutron stars. However, both the source-frame chirp mass $1.44^{+0.02}_{-0.02} M_{\odot}$ and the total mass $3.4^{+0.3}_{-0.1}\,M_{\odot}$ of this system are significantly larger than those of any other known binary neutron star system. The possibility that one or both binary components of the system are black holes cannot be ruled out from gravitational-wave data. We discuss possible origins of the system based on its inconsistency with the known Galactic binary neutron star population. Under the assumption that the signal was produced by a binary neutron star coalescence, the local rate of neutron star mergers is updated to $250-2810 \text{Gpc}^{-3}\text{yr}^{-1}$.}, number={1}, journal={The Astrophysical Journal Letters}, publisher={American Astronomical Society}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2020}, month={Mar}, pages={L3} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_agathos_et al._2020, title={GW190521: A Binary Black Hole Merger with a Total Mass of 
<mml:mrow><mml:mn>150}, volume={125}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/PhysRevLett.125.101102}, DOI={10.1103/PhysRevLett.125.101102}, abstractNote={On May 21, 2019 at 03:02:29 UTC Advanced LIGO and Advanced Virgo observed a short duration gravitational-wave signal, GW190521, with a three-detector network signal-to-noise ratio of 14.7, and an estimated false-alarm rate of 1 in 4900 yr using a search sensitive to generic transients. If GW190521 is from a quasicircular binary inspiral, then the detected signal is consistent with the merger of two black holes with masses of 85_{-14}^{+21} M_{⊙} and 66_{-18}^{+17} M_{⊙} (90% credible intervals). We infer that the primary black hole mass lies within the gap produced by (pulsational) pair-instability supernova processes, with only a 0.32% probability of being below 65 M_{⊙}. We calculate the mass of the remnant to be 142_{-16}^{+28} M_{⊙}, which can be considered an intermediate mass black hole (IMBH). The luminosity distance of the source is 5.3_{-2.6}^{+2.4} Gpc, corresponding to a redshift of 0.82_{-0.34}^{+0.28}. The inferred rate of mergers similar to GW190521 is 0.13_{-0.11}^{+0.30} Gpc^{-3} yr^{-1}.}, number={10}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and Agathos, M. and et al.}, year={2020}, month={Sep} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_agathos_et al._2020, title={GW190814: Gravitational Waves from the Coalescence of a 23 Solar Mass Black Hole with a 2.6 Solar Mass Compact Object}, volume={896}, ISSN={2041-8205 2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/ab960f}, DOI={10.3847/2041-8213/ab960f}, abstractNote={Abstract We report the observation of a compact binary coalescence involving a 22.2–24.3 M ⊙ black hole and a compact object with a mass of 2.50–2.67 M ⊙ (all measurements quoted at the 90% credible level). The gravitational-wave signal, GW190814, was observed during LIGO’s and Virgo’s third observing run on 2019 August 14 at 21:10:39 UTC and has a signal-to-noise ratio of 25 in the three-detector network. The source was localized to 18.5 deg 2 at a distance of <?CDATA ${241}_{-45}^{+41}$?> Mpc; no electromagnetic counterpart has been confirmed to date. The source has the most unequal mass ratio yet measured with gravitational waves, <?CDATA ${0.112}_{-0.009}^{+0.008}$?> , and its secondary component is either the lightest black hole or the heaviest neutron star ever discovered in a double compact-object system. The dimensionless spin of the primary black hole is tightly constrained to ≤0.07. Tests of general relativity reveal no measurable deviations from the theory, and its prediction of higher-multipole emission is confirmed at high confidence. We estimate a merger rate density of 1–23 Gpc −3 yr −1 for the new class of binary coalescence sources that GW190814 represents. Astrophysical models predict that binaries with mass ratios similar to this event can form through several channels, but are unlikely to have formed in globular clusters. However, the combination of mass ratio, component masses, and the inferred merger rate for this event challenges all current models of the formation and mass distribution of compact-object binaries.}, number={2}, journal={The Astrophysical Journal Letters}, publisher={American Astronomical Society}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and Agathos, M. and et al.}, year={2020}, month={Jun}, pages={L44} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adams_adhikari_adya_affeldt_et al._2020, title={Gravitational-wave Constraints on the Equatorial Ellipticity of Millisecond Pulsars}, volume={902}, ISSN={2041-8205 2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/abb655}, DOI={10.3847/2041-8213/abb655}, abstractNote={Abstract We present a search for continuous gravitational waves from five radio pulsars, comprising three recycled pulsars (PSR J0437−4715, PSR J0711−6830, and PSR J0737−3039A) and two young pulsars: the Crab pulsar (J0534+2200) and the Vela pulsar (J0835−4510). We use data from the third observing run of Advanced LIGO and Virgo combined with data from their first and second observing runs. For the first time, we are able to match (for PSR J0437−4715) or surpass (for PSR J0711−6830) the indirect limits on gravitational-wave emission from recycled pulsars inferred from their observed spin-downs, and constrain their equatorial ellipticities to be less than 10 −8 . For each of the five pulsars, we perform targeted searches that assume a tight coupling between the gravitational-wave and electromagnetic signal phase evolution. We also present constraints on PSR J0711−6830, the Crab pulsar, and the Vela pulsar from a search that relaxes this assumption, allowing the gravitational-wave signal to vary from the electromagnetic expectation within a narrow band of frequencies and frequency derivatives.}, number={1}, journal={The Astrophysical Journal Letters}, publisher={American Astronomical Society}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, A. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2020}, month={Oct}, pages={L21} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adya_affeldt_agathos_et al._2020, title={Model comparison from LIGO–Virgo data on GW170817’s binary components and consequences for the merger remnant}, volume={37}, ISSN={0264-9381 1361-6382}, url={http://dx.doi.org/10.1088/1361-6382/ab5f7c}, DOI={10.1088/1361-6382/ab5f7c}, abstractNote={GW170817 is the very first observation of gravitational waves originating from the coalescence of two compact objects in the mass range of neutron stars, accompanied by electromagnetic counterparts, and offers an opportunity to directly probe the internal structure of neutron stars. We perform Bayesian model selection on a wide range of theoretical predictions for the neutron star equation of state. For the binary neutron star hypothesis, we find that we cannot rule out the majority of theoretical models considered. In addition, the gravitational-wave data alone does not rule out the possibility that one or both objects were low-mass black holes. We discuss the possible outcomes in the case of a binary neutron star merger, finding that all scenarios from prompt collapse to long-lived or even stable remnants are possible. For long-lived remnants, we place an upper limit of 1.9 kHz on the rotation rate. If a black hole was formed any time after merger and the coalescing stars were slowly rotating, then the maximum baryonic mass of non-rotating neutron stars is at most 3.05 $M_\odot$, and three equations of state considered here can be ruled out. We obtain a tighter limit of 2.67 $M_\odot$ for the case that the merger results in a hypermassive neutron star.}, number={4}, journal={Classical and Quantum Gravity}, publisher={IOP Publishing}, author={Abbott, B P and Abbott, R and Abbott, T D and Abraham, S and Acernese, F and Ackley, K and Adams, C and Adya, V B and Affeldt, C and Agathos, M and et al.}, year={2020}, month={Jan}, pages={045006} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adya_affeldt_agathos_et al._2020, title={Optically targeted search for gravitational waves emitted by core-collapse supernovae during the first and second observing runs of advanced LIGO and advanced Virgo}, volume={101}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.101.084002}, DOI={10.1103/PhysRevD.101.084002}, abstractNote={We present the results from a search for gravitational-wave transients associated with core-collapse supernovae observed within a source distance of approximately 20 Mpc during the first and second observing runs of Advanced LIGO and Advanced Virgo. No significant gravitational-wave candidate was detected. We report the detection efficiencies as a function of the distance for waveforms derived from multidimensional numerical simulations and phenomenological extreme emission models. For neutrino-driven explosions the distance at which we reach 50% detection efficiency is approaching 5 kpc, and for magnetorotationally-driven explosions is up to 54 kpc. However, waveforms for extreme emission models are detectable up to 28 Mpc. For the first time, the gravitational-wave data enabled us to exclude part of the parameter spaces of two extreme emission models with confidence up to 83%, limited by coincident data coverage. Besides, using ad hoc harmonic signals windowed with Gaussian envelopes we constrained the gravitational-wave energy emitted during core-collapse at the levels of $4.27\times 10^{-4}\,M_\odot c^2$ and $1.28\times 10^{-1}\,M_\odot c^2$ for emissions at 235 Hz and 1304 Hz respectively. These constraints are two orders of magnitude more stringent than previously derived in the corresponding analysis using initial LIGO, initial Virgo and GEO 600 data.}, number={8}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adya, V. B. and Affeldt, C. and Agathos, M. and et al.}, year={2020}, month={Apr} }
 @article{abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_agathos_et al._2020, title={Properties and Astrophysical Implications of the 150 M<sub>⊙</sub> Binary Black Hole Merger GW190521}, volume={900}, ISSN={2041-8205 2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/aba493}, DOI={10.3847/2041-8213/aba493}, abstractNote={The gravitational-wave signal GW190521 is consistent with a binary black hole merger source at redshift 0.8 with unusually high component masses, $85^{+21}_{-14}\,M_{\odot}$ and $66^{+17}_{-18}\,M_{\odot}$, compared to previously reported events, and shows mild evidence for spin-induced orbital precession. The primary falls in the mass gap predicted by (pulsational) pair-instability supernova theory, in the approximate range $65 - 120\,M_{\odot}$. The probability that at least one of the black holes in GW190521 is in that range is 99.0%. The final mass of the merger $(142^{+28}_{-16}\,M_{\odot})$ classifies it as an intermediate-mass black hole. Under the assumption of a quasi-circular binary black hole coalescence, we detail the physical properties of GW190521's source binary and its post-merger remnant, including component masses and spin vectors. Three different waveform models, as well as direct comparison to numerical solutions of general relativity, yield consistent estimates of these properties. Tests of strong-field general relativity targeting the merger-ringdown stages of coalescence indicate consistency of the observed signal with theoretical predictions. We estimate the merger rate of similar systems to be $0.13^{+0.30}_{-0.11}\,{\rm Gpc}^{-3}\,\rm{yr}^{-1}$. We discuss the astrophysical implications of GW190521 for stellar collapse, and for the possible formation of black holes in the pair-instability mass gap through various channels: via (multiple) stellar coalescence, or via hierarchical merger of lower-mass black holes in star clusters or in active galactic nuclei. We find it to be unlikely that GW190521 is a strongly lensed signal of a lower-mass black hole binary merger. We also discuss more exotic possible sources for GW190521, including a highly eccentric black hole binary, or a primordial black hole binary.}, number={1}, journal={The Astrophysical Journal Letters}, publisher={American Astronomical Society}, author={Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and Agathos, M. and et al.}, year={2020}, month={Sep}, pages={L13} }
 @article{burns_goldstein_hui_blackburn_briggs_connaughton_hamburg_kocevski_veres_wilson-hodge_et al._2019, title={A Fermi Gamma-Ray Burst Monitor Search for Electromagnetic Signals Coincident with Gravitational-wave Candidates in Advanced LIGO's First Observing Run}, volume={871}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/aaf726}, DOI={10.3847/1538-4357/aaf726}, abstractNote={Abstract We present a search for prompt gamma-ray counterparts to compact binary coalescence gravitational wave (GW) candidates from Advanced LIGO’s first observing run (O1). As demonstrated by the multimessenger observations of GW170817/GRB 170817A, electromagnetic and GW observations provide complementary information about the astrophysical source, and in the case of weaker candidates, may strengthen the case for an astrophysical origin. Here we investigate low-significance GW candidates from the O1 compact binary coalescence searches using the Fermi Gamma-Ray Burst Monitor (GBM), leveraging its all sky and broad energy coverage. Candidates are ranked and compared to background to measure the significance. Those with false alarm rates (FARs) of less than 10 −5 Hz (about one per day, yielding a total of 81 candidates) are used as the search sample for gamma-ray follow-up. No GW candidates were found to be coincident with gamma-ray transients independently identified by blind searches of the GBM data. In addition, GW candidate event times were followed up by a separate targeted search of GBM data. Among the resulting GBM events, the two with the lowest FARs were the gamma-ray transient GW150914-GBM presented in Connaughton et al. and a solar flare in chance coincidence with a GW candidate.}, number={1}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Burns, E. and Goldstein, A. and Hui, C. M. and Blackburn, L. and Briggs, M. S. and Connaughton, V. and Hamburg, R. and Kocevski, D. and Veres, P. and Wilson-Hodge, C. A. and et al.}, year={2019}, month={Jan}, pages={90} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2019, title={All-sky search for continuous gravitational waves from isolated neutron stars using Advanced LIGO O2 data}, volume={100}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.100.024004}, DOI={10.1103/PhysRevD.100.024004}, abstractNote={We present results of an all-sky search for continuous gravitational waves (CWs), which can be produced by fast-spinning neutron stars with an asymmetry around their rotation axis, using data from the second observing run of the Advanced LIGO detectors. We employ three different semi-coherent methods ($\textit{FrequencyHough}$, $\textit{SkyHough}$, and $\textit{Time-Domain $\mathcal{F}$-statistic}$) to search in a gravitational-wave frequency band from 20 to 1922 Hz and a first frequency derivative from $-1\times10^{-8}$ to $2\times10^{-9}$ Hz/s. None of these searches has found clear evidence for a CW signal, so we present upper limits on the gravitational-wave strain amplitude $h_0$ (the lowest upper limit on $h_0$ is $1.7\times10^{-25}$ in the 123-124 Hz region) and discuss the astrophysical implications of this result. This is the most sensitive search ever performed over the broad range of parameters explored in this study.}, number={2}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2019}, month={Jul} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2019, title={All-sky search for long-duration gravitational-wave transients in the second Advanced LIGO observing run}, volume={99}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.99.104033}, DOI={10.1103/PhysRevD.99.104033}, abstractNote={We present the results of a search for long-duration gravitational-wave transients in the data from the Advanced LIGO second observation run; we search for gravitational-wave transients of $2~\text{--}~ 500$~s duration in the $24 - 2048$\,Hz frequency band with minimal assumptions about signal properties such as waveform morphologies, polarization, sky location or time of occurrence. Targeted signal models include fallback accretion onto neutron stars, broadband chirps from innermost stable circular orbit waves around rotating black holes, eccentric inspiral-merger-ringdown compact binary coalescence waveforms, and other models. The second observation run totals about \otwoduration~days of coincident data between November 2016 and August 2017. We find no significant events within the parameter space that we searched, apart from the already-reported binary neutron star merger GW170817. We thus report sensitivity limits on the root-sum-square strain amplitude $h_{\mathrm{rss}}$ at $50\%$ efficiency. These sensitivity estimates are an improvement relative to the first observing run and also done with an enlarged set of gravitational-wave transient waveforms. Overall, the best search sensitivity is $h_{\mathrm{rss}}^{50\%}$=$2.7\times10^{-22}$~$\mathrm{Hz^{-1/2}}$ for a millisecond magnetar model. For eccentric compact binary coalescence signals, the search sensitivity reaches $h_{\mathrm{rss}}^{50\%}$=$9.6\times10^{-22}$~$\mathrm{Hz^{-1/2}}$.}, number={10}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2019}, month={May} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2019, title={All-sky search for short gravitational-wave bursts in the second Advanced LIGO and Advanced Virgo run}, volume={100}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.100.024017}, DOI={10.1103/PhysRevD.100.024017}, abstractNote={We present the results of a search for short-duration gravitational-wave transients in the data from the second observing run of Advanced LIGO and Advanced Virgo. We search for gravitational-wave transients with a duration of milliseconds to approximately one second in the 32--4096 Hz frequency band with minimal assumptions about the signal properties, thus targeting a wide variety of sources. We also perform a matched-filter search for gravitational-wave transients from cosmic string cusps for which the waveform is well modeled. The unmodeled search detected gravitational waves from several binary black hole mergers which have been identified by previous analyses. No other significant events have been found by either the unmodeled search or the cosmic string search. We thus present the search sensitivities for a variety of signal waveforms and report upper limits on the source rate density as a function of the characteristic frequency of the signal. These upper limits are a factor of 3 lower than the first observing run, with a 50% detection probability for gravitational-wave emissions with energies of $\ensuremath{\sim}{10}^{\ensuremath{-}9}\text{ }\text{ }{M}_{\ensuremath{\bigodot}}{c}^{2}$ at 153 Hz. For the search dedicated to cosmic string cusps we consider several loop distribution models, and present updated constraints from the same search done in the first observing run.}, number={2}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2019}, month={Jul} }
 @misc{penn_kinley-hanlon_harry_macmillan_heu_follman_cole_deutsch_2019, title={Assessing Substrate-Transferred GaAs/AlGaAs Coatings for Gravitational-wave Detectors}, url={http://dx.doi.org/10.1364/OIC.2019.FA.3}, DOI={10.1364/OIC.2019.FA.3}, abstractNote={Substrate-transferred, 70-mm diameter AlGaAs coatings were tested for possible use in gravitational wave detectors by measuring the elastic loss [ϕbulk = (5.33±0.03)×10−4 and ϕ s h e a r = 0.0 − 0.0 + 5.2 × 10 − 7] and excess loss from bonding defects [≈ 5%].}, journal={Optical Interference Coatings Conference (OIC) 2019}, publisher={OSA}, author={Penn, Steven D. and Kinley-Hanlon, Maya M. and Harry, Gregory M. and MacMillan, Ian A. O. and Heu, Paula and Follman, David and Cole, Garrett D. and Deutsch, Christoph}, year={2019} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2019, title={Binary Black Hole Population Properties Inferred from the First and Second Observing Runs of Advanced LIGO and Advanced Virgo}, volume={882}, ISSN={2041-8205 2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/ab3800}, DOI={10.3847/2041-8213/ab3800}, abstractNote={We present results on the mass, spin, and redshift distributions with phenomenological population models using the ten binary black hole mergers detected in the first and second observing runs completed by Advanced LIGO and Advanced Virgo. We constrain properties of the binary black hole (BBH) mass spectrum using models with a range of parameterizations of the BBH mass and spin distributions. We find that the mass distribution of the more massive black hole in such binaries is well approximated by models with no more than 1% of black holes more massive than $45\,M_\odot$, and a power law index of $\alpha = {1.3}^{+1.4}_{-1.7}$ (90% credibility). We also show that BBHs are unlikely to be composed of black holes with large spins aligned to the orbital angular momentum. Modelling the evolution of the BBH merger rate with redshift, we show that it is at or increasing with redshift with 93% probability. Marginalizing over uncertainties in the BBH population, we find robust estimates of the BBH merger rate density of $R = {53.2}^{+55.8}_{-28.2}$ Gpc$^{-3}$ yr$^{-1}$ (90% credibility). As the BBH catalog grows in future observing runs, we expect that uncertainties in the population model parameters will shrink, potentially providing insights into the formation of black holes via supernovae, binary interactions of massive stars, stellar cluster dynamics, and the formation history of black holes across cosmic time.}, number={2}, journal={The Astrophysical Journal Letters}, publisher={American Astronomical Society}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2019}, month={Sep}, pages={L24} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2019, title={Constraining the 
<mml:mi>p
-Mode–
<mml:mi>g
-Mode Tidal Instability with GW170817}, volume={122}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/PhysRevLett.122.061104}, DOI={10.1103/PhysRevLett.122.061104}, abstractNote={We analyze the impact of a proposed tidal instability coupling p modes and g modes within neutron stars on GW170817. This nonresonant instability transfers energy from the orbit of the binary to internal modes of the stars, accelerating the gravitational-wave driven inspiral. We model the impact of this instability on the phasing of the gravitational wave signal using three parameters per star: an overall amplitude, a saturation frequency, and a spectral index. Incorporating these additional parameters, we compute the Bayes factor (lnB_{!pg}^{pg}) comparing our p-g model to a standard one. We find that the observed signal is consistent with waveform models that neglect p-g effects, with lnB_{!pg}^{pg}=0.03_{-0.58}^{+0.70} (maximum a posteriori and 90% credible region). By injecting simulated signals that do not include p-g effects and recovering them with the p-g model, we show that there is a ≃50% probability of obtaining similar lnB_{!pg}^{pg} even when p-g effects are absent. We find that the p-g amplitude for 1.4 M_{⊙} neutron stars is constrained to less than a few tenths of the theoretical maximum, with maxima a posteriori near one-tenth this maximum and p-g saturation frequency ∼70 Hz. This suggests that there are less than a few hundred excited modes, assuming they all saturate by wave breaking. For comparison, theoretical upper bounds suggest ≲10^{3} modes saturate by wave breaking. Thus, the measured constraints only rule out extreme values of the p-g parameters. They also imply that the instability dissipates ≲10^{51} erg over the entire inspiral, i.e., less than a few percent of the energy radiated as gravitational waves.}, number={6}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2019}, month={Feb} }
 @misc{cole_heu_follman_deutsch_macmillan_penn_kinley-hanlon_harry_2019, title={Crystalline Coating Loss Angle Measurement via Mechanical Ringdown on Large-Area Samples}, url={http://dx.doi.org/10.1109/FCS.2019.8856068}, DOI={10.1109/FCS.2019.8856068}, abstractNote={The elastic loss of ~70-mm diameter substrate-transferred crystalline coatings was measured via mechanical ringdown. The loss angles, decomposed into bulk and shear components, (5.33±0.03)×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> and <; 5.2)×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> respectively, were incorporated in a finite element model to predict the performance of a 35-mm long cavity with a 250-μm beam waist (radius), yielding a coating loss angle of (4.78±0.05)×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> , in agreement with published results from direct noise measurements, (4±4)×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> . This test independently confirms the low-noise performance of GaAs/AlGaAs multilayers and shows that the elastic loss is not degraded with size scaling.}, journal={2019 Joint Conference of the IEEE International Frequency Control Symposium and European Frequency and Time Forum (EFTF/IFC)}, publisher={IEEE}, author={Cole, G. D. and Heu, P. and Follman, D. and Deutsch, C. and MacMillan, I. A. O. and Penn, S. D. and Kinley-Hanlon, M. M. and Harry, G. M.}, year={2019}, month={Apr} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2019, title={Directional limits on persistent gravitational waves using data from Advanced LIGO’s first two observing runs}, volume={100}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.100.062001}, DOI={10.1103/PhysRevD.100.062001}, abstractNote={We perform an unmodeled search for persistent, directional gravitational wave (GW) sources using data from the first and second observing runs of Advanced LIGO. We do not find evidence for any GW signals. We place limits on the broadband GW flux emitted at 25 Hz from point sources with a power law spectrum at ${F}_{\ensuremath{\alpha},\mathrm{\ensuremath{\Theta}}}<(0.05--25)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}\text{ }\text{ }\mathrm{erg}\text{ }{\mathrm{cm}}^{\ensuremath{-}2}\text{ }{\mathrm{s}}^{\ensuremath{-}1}\text{ }{\mathrm{Hz}}^{\ensuremath{-}1}$ and the (normalized) energy density spectrum in GWs at 25 Hz from extended sources at ${\mathrm{\ensuremath{\Omega}}}_{\ensuremath{\alpha}}(\mathrm{\ensuremath{\Theta}})<(0.19--2.89)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}\text{ }\text{ }{\mathrm{sr}}^{\ensuremath{-}1}$ where $\ensuremath{\alpha}$ is the spectral index of the energy density spectrum. These represent improvements of $2.5--3\ifmmode\times\else\texttimes\fi{}$ over previous limits. We also consider point sources emitting GWs at a single frequency, targeting the directions of Sco X-1, SN 1987A, and the Galactic center. The best upper limits on the strain amplitude of a potential source in these three directions range from ${h}_{0}<(3.6--4.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}25}$, $1.5\ifmmode\times\else\texttimes\fi{}$ better than previous limits set with the same analysis method. We also report on a marginally significant outlier at 36.06 Hz. This outlier is not consistent with a persistent gravitational-wave source as its significance diminishes when combining all of the available data.}, number={6}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2019}, month={Sep} }
 @article{soares-santos_palmese_hartley_annis_garcia-bellido_lahav_doctor_fishbach_holz_lin_et al._2019, title={First Measurement of the Hubble Constant from a Dark Standard Siren using the Dark Energy Survey Galaxies and the LIGO/Virgo Binary–Black-hole Merger GW170814}, volume={876}, ISSN={2041-8205 2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/ab14f1}, DOI={10.3847/2041-8213/ab14f1}, abstractNote={Abstract We present a multi-messenger measurement of the Hubble constant H 0 using the binary–black-hole merger GW170814 as a standard siren, combined with a photometric redshift catalog from the Dark Energy Survey (DES). The luminosity distance is obtained from the gravitational wave signal detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo Collaboration (LVC) on 2017 August 14, and the redshift information is provided by the DES Year 3 data. Black hole mergers such as GW170814 are expected to lack bright electromagnetic emission to uniquely identify their host galaxies and build an object-by-object Hubble diagram. However, they are suitable for a statistical measurement, provided that a galaxy catalog of adequate depth and redshift completion is available. Here we present the first Hubble parameter measurement using a black hole merger. Our analysis results in <?CDATA ${H}_{0}={75}_{-32}^{+40}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$?> , which is consistent with both SN Ia and cosmic microwave background measurements of the Hubble constant. The quoted 68% credible region comprises 60% of the uniform prior range [20, 140] km s −1 Mpc −1 , and it depends on the assumed prior range. If we take a broader prior of [10, 220] km s −1 Mpc −1 , we find <?CDATA ${H}_{0}={78}_{-24}^{+96}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$?> (57% of the prior range). Although a weak constraint on the Hubble constant from a single event is expected using the dark siren method, a multifold increase in the LVC event rate is anticipated in the coming years and combinations of many sirens will lead to improved constraints on H 0 .}, number={1}, journal={The Astrophysical Journal Letters}, publisher={American Astronomical Society}, author={Soares-Santos, M. and Palmese, A. and Hartley, W. and Annis, J. and Garcia-Bellido, J. and Lahav, O. and Doctor, Z. and Fishbach, M. and Holz, D. E. and Lin, H. and et al.}, year={2019}, month={Apr}, pages={L7} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2019, title={GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs}, volume={9}, ISSN={2160-3308}, url={http://dx.doi.org/10.1103/PhysRevX.9.031040}, DOI={10.1103/PhysRevX.9.031040}, abstractNote={We present the results from three gravitational-wave searches for coalescing compact binaries with component masses above 1 M⊙ during the first and second observing runs of the advanced gravitational-wave detector network. During the first observing run (O1), from September 12, 2015 to January 19, 2016, gravitational waves from three binary black hole mergers were detected. The second observing run (O2), which ran from November 30, 2016 to August 25, 2017, saw the first detection of gravitational waves from a binary neutron star inspiral, in addition to the observation of gravitational waves from a total of seven binary black hole mergers, four of which we report here for the first time: GW170729, GW170809, GW170818, and GW170823. For all significant gravitational-wave events, we provide estimates of the source properties. The detected binary black holes have total masses between 18.6+3.2−0.7 M⊙ and 84.4+15.8−11.1 M⊙ and range in distance between 320+120−110 and 2840+1400−1360 Mpc. No neutron star–black hole mergers were detected. In addition to highly significant gravitational-wave events, we also provide a list of marginal event candidates with an estimated false-alarm rate less than 1 per 30 days. From these results over the first two observing runs, which include approximately one gravitational-wave detection per 15 days of data searched, we infer merger rates at the 90% confidence intervals of 110−3840 Gpc−3 y−1 for binary neutron stars and 9.7−101 Gpc−3 y−1 for binary black holes assuming fixed population distributions and determine a neutron star–black hole merger rate 90% upper limit of 610 Gpc−3 y−1.10 MoreReceived 14 December 2018Revised 27 March 2019DOI:https://doi.org/10.1103/PhysRevX.9.031040Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Gravitational wave sourcesResearch AreasGravitationGravitational wavesGravitational wave sourcesResearch AreasGravitational wave detectionGravitational wave sourcesGravitational wavesGravitation, Cosmology & Astrophysics}, number={3}, journal={Physical Review X}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2019}, month={Sep} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2019, title={Low-latency Gravitational-wave Alerts for Multimessenger Astronomy during the Second Advanced LIGO and Virgo Observing Run}, volume={875}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/ab0e8f}, DOI={10.3847/1538-4357/ab0e8f}, abstractNote={Advanced LIGO's second observing run (O2), conducted from November 30, 2016 to August 25, 2017, combined with Advanced Virgo's first observations in August 2017 witnessed the birth of gravitational-wave multi-messenger astronomy. The first ever gravitational-wave detection from the coalescence of two neutron stars, GW170817, and its gamma-ray counterpart, GRB 170817A, led to an electromagnetic follow-up of the event at an unprecedented scale. Several teams from across the world searched for EM/neutrino counterparts to GW170817, paving the way for the discovery of optical, X-ray, and radio counterparts. In this article, we describe the online identification of gravitational-wave transients and the distribution of gravitational-wave alerts by the LIGO and Virgo collaborations during O2. We also describe the gravitational-wave observables which were sent in the alerts to enable searches for their counterparts. Finally, we give an overview of the online candidate alerts shared with observing partners during O2. Alerts were issued for 14 candidates, six of which have been confirmed as gravitational-wave events associated with the merger of black holes or neutron stars. Eight of the 14 alerts were issued less than an hour after data acquisition.}, number={2}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2019}, month={Apr}, pages={161} }
 @article{penn_kinley-hanlon_macmillan_heu_follman_deutsch_cole_harry_2019, title={Mechanical ringdown studies of large-area substrate-transferred GaAs/AlGaAs crystalline coatings}, volume={36}, ISSN={0740-3224 1520-8540}, url={http://dx.doi.org/10.1364/josab.36.000c15}, DOI={10.1364/josab.36.000c15}, abstractNote={We investigated elastic loss in GaAs/AlGaAs multilayers to help determine the suitability of these coatings for future gravitational wave detectors. We measured large ($\approx 70$-mm diameter) substrate-transferred crystalline coating samples with an improved substrate polish and bonding method. The elastic loss, when decomposed into bulk and shear contributions, was shown to arise entirely from the bulk loss, $\phi_{\mathrm{Bulk}} = (5.33 \pm 0.03)\times 10^{-4}$, with $\phi_{\mathrm{Shear}} = (0.0 \pm 5.2) \times 10^{-7}$. These results predict the coating loss of an 8-mm diameter coating in a 35-mm long cavity with a 250-$\mu$m spot size (radius) to be $\phi_{\mathrm{coating}} = (4.78 \pm 0.05) \times 10^{-5}$, in agreement with the published result from direct thermal noise measurement of $\phi_{\mathrm{coating}} = (4 \pm 4) \times 10^{-5}$. Bonding defects were shown to have little impact on the overall elastic loss.}, number={4}, journal={Journal of the Optical Society of America B}, publisher={The Optical Society}, author={Penn, Steven D. and Kinley-Hanlon, Maya M. and MacMillan, Ian A. O. and Heu, Paula and Follman, David and Deutsch, Christoph and Cole, Garrett D. and Harry, Gregory M.}, year={2019}, month={Feb}, pages={C15} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2019, title={Narrow-band search for gravitational waves from known pulsars using the second LIGO observing run}, volume={99}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.99.122002}, DOI={10.1103/PhysRevD.99.122002}, abstractNote={Isolated spinning neutron stars, asymmetric with respect to their rotation axis, are expected to be sources of continuous gravitational waves. The most sensitive searches for these sources are based on accurate matched filtering techniques that assume the continuous wave to be phase locked with the pulsar beamed emission. While matched filtering maximizes the search sensitivity, a significant signal-to-noise ratio loss will happen in the case of a mismatch between the assumed and the true signal phase evolution. Narrow-band algorithms allow for a small mismatch in the frequency and spin-down values of the pulsar while coherently integrating the entire dataset. In this paper, we describe a narrow-band search using LIGO O2 data for the continuous wave emission of 33 pulsars. No evidence of a continuous wave signal is found, and upper limits on the gravitational wave amplitude over the analyzed frequency and spin-down ranges are computed for each of the targets. In this search, we surpass the spin-down limit, namely, the maximum rotational energy loss due to gravitational waves emission for some of the pulsars already present in the LIGO O1 narrow-band search, such as $\mathrm{J}1400\ensuremath{-}6325$, $\mathrm{J}1813\ensuremath{-}1246$, $\mathrm{J}1833\ensuremath{-}1034$, $\mathrm{J}1952+3252$, and for new targets such as $\mathrm{J}0940\ensuremath{-}5428$ and $\mathrm{J}1747\ensuremath{-}2809$. For $\mathrm{J}1400\ensuremath{-}6325$, $\mathrm{J}1833\ensuremath{-}1034$, and $\mathrm{J}1747\ensuremath{-}2809$, this is the first time the spin-down limit is surpassed.}, number={12}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2019}, month={Jun} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2019, title={Properties of the Binary Neutron Star Merger GW170817}, volume={9}, ISSN={2160-3308}, url={http://dx.doi.org/10.1103/PhysRevX.9.011001}, DOI={10.1103/PhysRevX.9.011001}, abstractNote={On August 17, 2017, the Advanced LIGO and Advanced Virgo gravitational-wave detectors observed a low-mass compact binary inspiral. The initial sky localization of the source of the gravitational-wave signal, GW170817, allowed electromagnetic observatories to identify NGC 4993 as the host galaxy. In this work, we improve initial estimates of the binary’s properties, including component masses, spins, and tidal parameters, using the known source location, improved modeling, and recalibrated Virgo data. We extend the range of gravitational-wave frequencies considered down to 23 Hz, compared to 30 Hz in the initial analysis. We also compare results inferred using several signal models, which are more accurate and incorporate additional physical effects as compared to the initial analysis. We improve the localization of the gravitational-wave source to a 90% credible region of 16 deg2. We find tighter constraints on the masses, spins, and tidal parameters, and continue to find no evidence for nonzero component spins. The component masses are inferred to lie between 1.00 and 1.89 M⊙ when allowing for large component spins, and to lie between 1.16 and 1.60 M⊙ (with a total mass 2.73+0.04−0.01 M⊙) when the spins are restricted to be within the range observed in Galactic binary neutron stars. Using a precessing model and allowing for large component spins, we constrain the dimensionless spins of the components to be less than 0.50 for the primary and 0.61 for the secondary. Under minimal assumptions about the nature of the compact objects, our constraints for the tidal deformability parameter ˜Λ are (0,630) when we allow for large component spins, and 300+420−230 (using a 90% highest posterior density interval) when restricting the magnitude of the component spins, ruling out several equation-of-state models at the 90% credible level. Finally, with LIGO and GEO600 data, we use a Bayesian analysis to place upper limits on the amplitude and spectral energy density of a possible postmerger signal.8 MoreReceived 6 June 2018Revised 20 September 2018Corrected 30 April 2019DOI:https://doi.org/10.1103/PhysRevX.9.011001Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasGravitational wavesPhysical SystemsBinary starsNeutron stars & pulsarsPropertiesAstronomical masses & mass distributionsComposition of astronomical objectsDistances, redshifts, & velocitiesGravitation, Cosmology & Astrophysics}, number={1}, journal={Physical Review X}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2019}, month={Jan} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2019, title={Search for Eccentric Binary Black Hole Mergers with Advanced LIGO and Advanced Virgo during Their First and Second Observing Runs}, volume={883}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/ab3c2d}, DOI={10.3847/1538-4357/ab3c2d}, abstractNote={Abstract When formed through dynamical interactions, stellar-mass binary black holes (BBHs) may retain eccentric orbits ( e > 0.1 at 10 Hz) detectable by ground-based gravitational-wave detectors. Eccentricity can therefore be used to differentiate dynamically formed binaries from isolated BBH mergers. Current template-based gravitational-wave searches do not use waveform models associated with eccentric orbits, rendering the search less efficient for eccentric binary systems. Here we present the results of a search for BBH mergers that inspiral in eccentric orbits using data from the first and second observing runs (O1 and O2) of Advanced LIGO and Advanced Virgo. We carried out the search with the coherent WaveBurst algorithm, which uses minimal assumptions on the signal morphology and does not rely on binary waveform templates. We show that it is sensitive to binary mergers with a detection range that is weakly dependent on eccentricity for all bound systems. Our search did not identify any new binary merger candidates. We interpret these results in light of eccentric binary formation models. We rule out formation channels with rates ≳100 Gpc −3 yr −1 for e > 0.1, assuming a black hole mass spectrum with a power-law index ≲2.}, number={2}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2019}, month={Sep}, pages={149} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2019, title={Search for Gravitational Waves from a Long-lived Remnant of the Binary Neutron Star Merger GW170817}, volume={875}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/ab0f3d}, DOI={10.3847/1538-4357/ab0f3d}, abstractNote={One unanswered question about the binary neutron star coalescence GW170817 is the nature of its post-merger remnant. A previous search for post-merger gravitational waves targeted high-frequency signals from a possible neutron star remnant with a maximum signal duration of 500 s. Here we revisit the neutron star remnant scenario with a focus on longer signal durations up until the end of the Second Advanced LIGO-Virgo Observing run, 8.5 days after the coalescence of GW170817. The main physical scenario for such emission is the power-law spindown of a massive magnetar-like remnant. We use four independent search algorithms with varying degrees of restrictiveness on the signal waveformand different ways of dealing with noise artefacts. In agreement with theoretical estimates, we find no significant signal candidates. Through simulated signals, we quantify that with the current detector sensitivity, nowhere in the studied parameter space are we sensitive to a signal from more than 1 Mpc away, compared to the actual distance of 40 Mpc. This study however serves as a prototype for post-merger analyses in future observing runs with expected higher sensitivity.}, number={2}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2019}, month={Apr}, pages={160} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2019, title={Search for Gravitational-wave Signals Associated with Gamma-Ray Bursts during the Second Observing Run of Advanced LIGO and Advanced Virgo}, volume={886}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/ab4b48}, DOI={10.3847/1538-4357/ab4b48}, abstractNote={Abstract We present the results of targeted searches for gravitational-wave transients associated with gamma-ray bursts during the second observing run of Advanced LIGO and Advanced Virgo, which took place from 2016 November to 2017 August. We have analyzed 98 gamma-ray bursts using an unmodeled search method that searches for generic transient gravitational waves and 42 with a modeled search method that targets compact-binary mergers as progenitors of short gamma-ray bursts. Both methods clearly detect the previously reported binary merger signal GW170817, with p -values of <9.38 × 10 −6 (modeled) and 3.1 × 10 −4 (unmodeled). We do not find any significant evidence for gravitational-wave signals associated with the other gamma-ray bursts analyzed, and therefore we report lower bounds on the distance to each of these, assuming various source types and signal morphologies. Using our final modeled search results, short gamma-ray burst observations, and assuming binary neutron star progenitors, we place bounds on the rate of short gamma-ray bursts as a function of redshift for z ≤ 1. We estimate 0.07–1.80 joint detections with Fermi -GBM per year for the 2019–20 LIGO-Virgo observing run and 0.15–3.90 per year when current gravitational-wave detectors are operating at their design sensitivities.}, number={1}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2019}, month={Nov}, pages={75} }
 @article{albert_andré_anghinolfi_ardid_aubert_aublin_avgitas_baret_barrios-martí_basa_et al._2019, title={Search for Multimessenger Sources of Gravitational Waves and High-energy Neutrinos with Advanced LIGO during Its First Observing Run, ANTARES, and IceCube}, volume={870}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/aaf21d}, DOI={10.3847/1538-4357/aaf21d}, abstractNote={Astrophysical sources of gravitational waves, such as binary neutron star and black hole mergers or core-collapse supernovae, can drive relativistic outflows, giving rise to non-thermal high-energy emission. High-energy neutrinos are signatures of such outflows. The detection of gravitational waves and high-energy neutrinos from common sources could help establish the connection between the dynamics of the progenitor and the properties of the outflow. We searched for associated emission of gravitational waves and high-energy neutrinos from astrophysical transients with minimal assumptions using data from Advanced LIGO from its first observing run O1, and data from the ANTARES and IceCube neutrino observatories from the same time period. We focused on candidate events whose astrophysical origin could not be determined from a single messenger. We found no significant coincident candidate, which we used to constrain the rate density of astrophysical sources dependent on their gravitational wave and neutrino emission processes.}, number={2}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Albert, A. and André, M. and Anghinolfi, M. and Ardid, M. and Aubert, J.-J. and Aublin, J. and Avgitas, T. and Baret, B. and Barrios-Martí, J. and Basa, S. and et al.}, year={2019}, month={Jan}, pages={134} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2019, title={Search for Subsolar Mass Ultracompact Binaries in Advanced LIGO’s Second Observing Run}, volume={123}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/PhysRevLett.123.161102}, DOI={10.1103/PhysRevLett.123.161102}, abstractNote={We present an Advanced LIGO and Advanced Virgo search for sub-solar mass ultracompact objects in data obtained during Advanced LIGO's second observing run. In contrast to a previous search of Advanced LIGO data from the first observing run, this search includes the effects of component spin on the gravitational waveform. We identify no viable gravitational wave candidates consistent with sub-solar mass ultracompact binaries with at least one component between 0.2 - 1.0 solar masses. We use the null result to constrain the binary merger rate of (0.2 solar mass, 0.2 solar mass) binaries to be less than 3.7 x 10^5 Gpc^-3 yr^-1 and the binary merger rate of (1.0 solar mass, 1.0 solar mass) binaries to be less than 5.2 x 10^3 Gpc^-3 yr^-1. Sub-solar mass ultracompact objects are not expected to form via known stellar evolution channels, though it has been suggested that primordial density fluctuations or particle dark matter with cooling mechanisms and/or nuclear interactions could form black holes with sub-solar masses. Assuming a particular primordial black hole formation model, we constrain a population of merging 0.2 solar mass black holes to account for less than 16% of the dark matter density and a population of merging 1.0 solar mass black holes to account for less than 2% of the dark matter density. We discuss how constraints on the merger rate and dark matter fraction may be extended to arbitrary black hole population models that predict sub-solar mass binaries.}, number={16}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2019}, month={Oct} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2019, title={Search for Transient Gravitational-wave Signals Associated with Magnetar Bursts during Advanced LIGO’s Second Observing Run}, volume={874}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/ab0e15}, DOI={10.3847/1538-4357/ab0e15}, abstractNote={Abstract We present the results of a search for short- and intermediate-duration gravitational-wave signals from four magnetar bursts in Advanced LIGO’s second observing run. We find no evidence of a signal and set upper bounds on the root sum squared of the total dimensionless strain ( h rss ) from incoming intermediate-duration gravitational waves ranging from 1.1 × 10 −22 at 150 Hz to 4.4 × 10 −22 at 1550 Hz at 50% detection efficiency. From the known distance to the magnetar SGR 1806–20 (8.7 kpc), we can place upper bounds on the isotropic gravitational-wave energy of 3.4 × 10 44 erg at 150 Hz assuming optimal orientation. This represents an improvement of about a factor of 10 in strain sensitivity from the previous search for such signals, conducted during initial LIGO’s sixth science run. The short-duration search yielded upper limits of 2.1 × 10 44 erg for short white noise bursts, and 2.3 × 10 47 erg for 100 ms long ringdowns at 1500 Hz, both at 50% detection efficiency.}, number={2}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2019}, month={Apr}, pages={163} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2019, title={Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model}, volume={100}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.100.122002}, DOI={10.1103/PhysRevD.100.122002}, abstractNote={We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO's second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h095%=3.47×10−25 when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering.Received 28 June 2019DOI:https://doi.org/10.1103/PhysRevD.100.122002© 2019 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasGravitational wavesGravitation, Cosmology & Astrophysics}, number={12}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2019}, month={Dec} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adams_adhikari_adya_et al._2019, title={Search for intermediate mass black hole binaries in the first and second observing runs of the Advanced LIGO and Virgo network}, volume={100}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.100.064064}, DOI={10.1103/PhysRevD.100.064064}, abstractNote={Gravitational wave astronomy has been firmly established with the detection of gravitational waves from the merger of ten stellar mass binary black holes and a neutron star binary. This paper reports on the all-sky search for gravitational waves from intermediate mass black hole binaries in the first and second observing runs of the Advanced LIGO and Virgo network. The search uses three independent algorithms: two based on matched filtering of the data with waveform templates of gravitational wave signals from compact binaries, and a third, model-independent algorithm that employs no signal model for the incoming signal. No intermediate mass black hole binary event was detected in this search. Consequently, we place upper limits on the merger rate density for a family of intermediate mass black hole binaries. In particular, we choose sources with total masses $M=m_1+m_2\in[120,800]$M$_\odot$ and mass ratios $q = m_2/m_1 \in[0.1,1.0]$. For the first time, this calculation is done using numerical relativity waveforms (which include higher modes) as models of the real emitted signal. We place a most stringent upper limit of $0.20$~Gpc$^{-3}$yr$^{-1}$ (in co-moving units at the 90% confidence level) for equal-mass binaries with individual masses $m_{1,2}=100$M$_\odot$ and dimensionless spins $\chi_{1,2}= 0.8$ aligned with the orbital angular momentum of the binary. This improves by a factor of $\sim 5$ that reported after Advanced LIGO's first observing run.}, number={6}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, A. and Adams, C. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2019}, month={Sep} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adya_affeldt_agathos_et al._2019, title={Search for the isotropic stochastic background using data from Advanced LIGO’s second observing run}, volume={100}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.100.061101}, DOI={10.1103/PhysRevD.100.061101}, abstractNote={The stochastic gravitational-wave background is a superposition of sources that are either too weak or too numerous to detect individually. In this study, we present the results from a cross-correlation analysis on data from Advanced LIGO's second observing run (O2), which we combine with the results of the first observing run (O1). We do not find evidence for a stochastic background, so we place upper limits on the normalized energy density in gravitational waves at the 95% credible level of ${\mathrm{\ensuremath{\Omega}}}_{\mathrm{GW}}<6.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$ for a frequency-independent (flat) background and ${\mathrm{\ensuremath{\Omega}}}_{\mathrm{GW}}<4.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$ at 25 Hz for a background of compact binary coalescences. The upper limit improves over the O1 result by a factor of 2.8. Additionally, we place upper limits on the energy density in an isotropic background of scalar- and vector-polarized gravitational waves, and we discuss the implication of these results for models of compact binaries and cosmic string backgrounds. Finally, we present a conservative estimate of the correlated broadband noise due to the magnetic Schumann resonances in O2, based on magnetometer measurements at both the LIGO Hanford and LIGO Livingston observatories. We find that correlated noise is well below the O2 sensitivity.}, number={6}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adya, V. B. and Affeldt, C. and Agathos, M. and et al.}, year={2019}, month={Sep} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2019, title={Searches for Continuous Gravitational Waves from 15 Supernova Remnants and Fomalhaut b with Advanced LIGO<sup>*}, volume={875}, ISSN={0004-637X 1538-4357}, url={http://dx.doi.org/10.3847/1538-4357/ab113b}, DOI={10.3847/1538-4357/ab113b}, abstractNote={We describe directed searches for continuous gravitational waves from sixteen well localized candidate neutron stars assuming none of the stars has a binary companion. The searches were directed toward fifteen supernova remnants and Fomalhaut~b, an extrasolar planet candidate which has been suggested to be a nearby old neutron star. Each search covered a broad band of frequencies and first and second time derivatives. After coherently integrating spans of data from the first Advanced LIGO observing run of 3.5--53.7 days per search, applying data-based vetoes and discounting known instrumental artifacts, we found no astrophysical signals. We set upper limits on intrinsic gravitational wave strain as strict as $1\times10^{-25}$, on fiducial neutron star ellipticity as strict as $2\times10^{-9}$, and on fiducial $r$-mode amplitude as strict as $3\times10^{-8}$.}, number={2}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2019}, month={Apr}, pages={122} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2019, title={Tests of General Relativity with GW170817}, volume={123}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/PhysRevLett.123.011102}, DOI={10.1103/PhysRevLett.123.011102}, abstractNote={The recent discovery by Advanced LIGO and Advanced Virgo of a gravitational wave signal from a binary neutron star inspiral has enabled tests of general relativity (GR) with this new type of source. This source, for the first time, permits tests of strong-field dynamics of compact binaries in the presence of matter. In this Letter, we place constraints on the dipole radiation and possible deviations from GR in the post-Newtonian coefficients that govern the inspiral regime. Bounds on modified dispersion of gravitational waves are obtained; in combination with information from the observed electromagnetic counterpart we can also constrain effects due to large extra dimensions. Finally, the polarization content of the gravitational wave signal is studied. The results of all tests performed here show good agreement with GR.Received 20 November 2018Revised 21 March 2019Corrected 20 August 2019DOI:https://doi.org/10.1103/PhysRevLett.123.011102© 2019 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAlternative gravity theoriesExperimental studies of gravityGamma ray burstsGeneral relativityGravitationGravitational wavesGravity in dimensions other than fourGravitation, Cosmology & Astrophysics}, number={1}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2019}, month={Jul} }
 @article{abbott_abbott_abbott_abraham_acernese_ackley_adams_adhikari_adya_affeldt_et al._2019, title={Tests of general relativity with the binary black hole signals from the LIGO-Virgo catalog GWTC-1}, volume={100}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.100.104036}, DOI={10.1103/PhysRevD.100.104036}, abstractNote={The detection of gravitational waves by Advanced LIGO and Advanced Virgo provides an opportunity to test general relativity in a regime that is inaccessible to traditional astronomical observations and laboratory tests. We present four tests of the consistency of the data with binary black hole gravitational waveforms predicted by general relativity. One test subtracts the best-fit waveform from the data and checks the consistency of the residual with detector noise. The second test checks the consistency of the low- and high-frequency parts of the observed signals. The third test checks that phenomenological deviations introduced in the waveform model (including in the post-Newtonian coefficients) are consistent with zero. The fourth test constrains modifications to the propagation of gravitational waves due to a modified dispersion relation, including that from a massive graviton. We present results both for individual events and also results obtained by combining together particularly strong events from the first and second observing runs of Advanced LIGO and Advanced Virgo, as collected in the catalog GWTC-1. We do not find any inconsistency of the data with the predictions of general relativity and improve our previously presented combined constraints by factors of 1.1 to 2.5. In particular, we bound the mass of the graviton to be $m_g \leq 4.7 \times 10^{-23} \text{eV}/c^2$ ($90\%$ credible level), an improvement of a factor of 1.6 over our previously presented results. Additionally, we check that the four gravitational-wave events published for the first time in GWTC-1 do not lead to stronger constraints on alternative polarizations than those published previously.}, number={10}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abraham, S. and Acernese, F. and Ackley, K. and Adams, C. and Adhikari, R. X. and Adya, V. B. and Affeldt, C. and et al.}, year={2019}, month={Nov} }
 @article{koch_cole_deutsch_follman_heu_kinley-hanlon_kirchhoff_leavey_lehmann_oppermann_et al._2019, title={Thickness uniformity measurements and damage threshold tests of large-area GaAs/AlGaAs crystalline coatings for precision interferometry}, volume={27}, ISSN={1094-4087}, url={http://dx.doi.org/10.1364/oe.27.036731}, DOI={10.1364/OE.27.036731}, abstractNote={Precision interferometry is the leading method for extremely sensitive measurements in gravitational wave astronomy.Thermal noise of dielectric coatings poses a limitation to the sensitivity of these interferometers.To decrease coating thermal noise, new crystalline GaAs/AlGaAs multilayer mirrors have been developed.To date, the surface figure and thickness uniformity of these alternative low-loss coatings has not been investigated.Surface figure errors, for example, cause small angle scattering and thereby limit the sensitivity of an interferometer.Here we measure the surface figure of highly reflective, substrate-transferred, crystalline GaAs/AlGaAs coatings with a custom scanning reflectance system.We exploit the fact that the reflectivity varies with the thickness of the coating.To increase penetration into the coating, we used a 1550 nm laser on a highly reflective coating designed for a center wavelength of 1064 nm.The RMS thickness variation of a two inch optic was measured to be 0.41 ± 0.05 nm.This result is within 10% of the thickness uniformity, of 0.37 nm RMS, achieved with ion-beam sputtered coatings for the aLIGO detector.We additionally measured a lower limit of the laser induced damage threshold of 64 MW/cm 2 for GaAs/AlGaAs coatings at a wavelength of 1064 nm.}, number={25}, journal={Optics Express}, publisher={The Optical Society}, author={Koch, P. and Cole, G. D. and Deutsch, C. and Follman, D. and Heu, P. and Kinley-Hanlon, M. and Kirchhoff, R. and Leavey, S. and Lehmann, J. and Oppermann, P. and et al.}, year={2019}, month={Dec}, pages={36731} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2018, title={Full band all-sky search for periodic gravitational waves in the O1 LIGO data}, url={http://hdl.handle.net/11568/923645}, DOI={10.1103/PhysRevD.97.102003}, abstractNote={We report on a new all-sky search for periodic gravitational waves in the frequency band 475--2000 Hz and with a frequency time derivative in the range of $[\ensuremath{-}1.0,+0.1]\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}8}\text{ }\mathrm{Hz}/\mathrm{s}$. Potential signals could be produced by a nearby spinning and slightly nonaxisymmetric isolated neutron star in our Galaxy. This search uses the data from Advanced LIGO's first observational run O1. No gravitational-wave signals were observed, and upper limits were placed on their strengths. For completeness, results from the separately published low-frequency search 20--475 Hz are included as well. Our lowest upper limit on worst-case (linearly polarized) strain amplitude ${h}_{0}$ is $\ensuremath{\sim}4\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}25}$ near 170 Hz, while at the high end of our frequency range, we achieve a worst-case upper limit of $1.3\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}24}$. For a circularly polarized source (most favorable orientation), the smallest upper limit obtained is $\ensuremath{\sim}1.5\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}25}$.}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2018} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2018, title={GW170817: Implications for the Stochastic Gravitational-Wave Background from Compact Binary Coalescences}, volume={120}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/PhysRevLett.120.091101}, DOI={10.1103/PhysRevLett.120.091101}, abstractNote={The LIGO Scientific and Virgo Collaborations have announced the event GW170817, the first detection of gravitational waves from the coalescence of two neutron stars. The merger rate of binary neutron stars estimated from this event suggests that distant, unresolvable binary neutron stars create a significant astrophysical stochastic gravitational-wave background. The binary neutron star component will add to the contribution from binary black holes, increasing the amplitude of the total astrophysical background relative to previous expectations. In the Advanced LIGO-Virgo frequency band most sensitive to stochastic backgrounds (near 25 Hz), we predict a total astrophysical background with amplitude Ω_{GW}(f=25 Hz)=1.8_{-1.3}^{+2.7}×10^{-9} with 90% confidence, compared with Ω_{GW}(f=25 Hz)=1.1_{-0.7}^{+1.2}×10^{-9} from binary black holes alone. Assuming the most probable rate for compact binary mergers, we find that the total background may be detectable with a signal-to-noise-ratio of 3 after 40 months of total observation time, based on the expected timeline for Advanced LIGO and Virgo to reach their design sensitivity.}, number={9}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2018}, month={Feb} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2018, title={GW170817: Measurements of Neutron Star Radii and Equation of State}, volume={121}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/PhysRevLett.121.161101}, DOI={10.1103/PhysRevLett.121.161101}, abstractNote={On 17 August 2017, the LIGO and Virgo observatories made the first direct detection of gravitational waves from the coalescence of a neutron star binary system. The detection of this gravitational-wave signal, GW170817, offers a novel opportunity to directly probe the properties of matter at the extreme conditions found in the interior of these stars. The initial, minimal-assumption analysis of the LIGO and Virgo data placed constraints on the tidal effects of the coalescing bodies, which were then translated to constraints on neutron star radii. Here, we expand upon previous analyses by working under the hypothesis that both bodies were neutron stars that are described by the same equation of state and have spins within the range observed in Galactic binary neutron stars. Our analysis employs two methods: the use of equation-of-state-insensitive relations between various macroscopic properties of the neutron stars and the use of an efficient parametrization of the defining function p(ρ) of the equation of state itself. From the LIGO and Virgo data alone and the first method, we measure the two neutron star radii as R_{1}=10.8_{-1.7}^{+2.0} km for the heavier star and R_{2}=10.7_{-1.5}^{+2.1} km for the lighter star at the 90% credible level. If we additionally require that the equation of state supports neutron stars with masses larger than 1.97 M_{⊙} as required from electromagnetic observations and employ the equation-of-state parametrization, we further constrain R_{1}=11.9_{-1.4}^{+1.4} km and R_{2}=11.9_{-1.4}^{+1.4} km at the 90% credible level. Finally, we obtain constraints on p(ρ) at supranuclear densities, with pressure at twice nuclear saturation density measured at 3.5_{-1.7}^{+2.7}×10^{34} dyn cm^{-2} at the 90% level.}, number={16}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2018}, month={Oct} }
 @article{penn_kinley-hanlon_macmillan_heu_follman_deutsch_cole_harry_2018, title={Mechanical Ringdown Studies of Large-Area Substrate-Transferred GaAs/AlGaAs Crystalline Coatings ...}, url={https://dx.doi.org/10.48550/arxiv.1811.05976}, DOI={10.48550/arxiv.1811.05976}, author={Penn, Steven D. and Kinley-Hanlon, Maya M. and MacMillan, Ian A. O. and Heu, Paula and Follman, David and Deutsch, Christoph and Cole, Garrett D. and Harry, Gregory M.}, year={2018} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2018, title={Search for Subsolar-Mass Ultracompact Binaries in Advanced LIGO’s First Observing Run}, volume={121}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/PhysRevLett.121.231103}, DOI={10.1103/PhysRevLett.121.231103}, abstractNote={We present the first Advanced LIGO and Advanced Virgo search for ultracompact binary systems with component masses between $0.2\text{ }\text{ }{M}_{\ensuremath{\bigodot}}--1.0\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ using data taken between September 12, 2015 and January 19, 2016. We find no viable gravitational wave candidates. Our null result constrains the coalescence rate of monochromatic (delta function) distributions of nonspinning ($0.2\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$, $0.2\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$) ultracompact binaries to be less than $1.0\ifmmode\times\else\texttimes\fi{}{10}^{6}\text{ }\text{ }{\mathrm{Gpc}}^{\ensuremath{-}3}\text{ }\text{ }{\mathrm{yr}}^{\ensuremath{-}1}$ and the coalescence rate of a similar distribution of ($1.0\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$, $1.0\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$) ultracompact binaries to be less than $1.9\ifmmode\times\else\texttimes\fi{}{10}^{4}\text{ }\text{ }{\mathrm{Gpc}}^{\ensuremath{-}3}\text{ }\text{ }{\mathrm{yr}}^{\ensuremath{-}1}$ (at 90% confidence). Neither black holes nor neutron stars are expected to form below $\ensuremath{\sim}1\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ through conventional stellar evolution, though it has been proposed that similarly low mass black holes could be formed primordially through density fluctuations in the early Universe and contribute to the dark matter density. The interpretation of our constraints in the primordial black hole dark matter paradigm is highly model dependent; however, under a particular primordial black hole binary formation scenario we constrain monochromatic primordial black hole populations of $0.2\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ to be less than 33% of the total dark matter density and monochromatic populations of $1.0\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ to be less than 5% of the dark matter density. The latter strengthens the presently placed bounds from microlensing surveys of massive compact halo objects (MACHOs) provided by the MACHO and EROS Collaborations.}, number={23}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2018}, month={Dec} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2018, title={Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background}, url={http://hdl.handle.net/11588/738014}, DOI={10.1103/PhysRevLett.120.201102}, abstractNote={The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω_{0}^{T}<5.58×10^{-8}, Ω_{0}^{V}<6.35×10^{-8}, and Ω_{0}^{S}<1.08×10^{-7} at a reference frequency f_{0}=25 Hz.}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2018} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2018, title={Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background}, url={http://hdl.handle.net/11568/923643}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2018} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2018, title={Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background}, url={http://hdl.handle.net/21.11116/0000-0000-BA40-6}, author={Abbott, B. and Abbott, R. and Abbott, T. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. and Adya, V. and et al.}, year={2018} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2017, title={A gravitational-wave standard siren measurement of the Hubble constant}, volume={551}, ISSN={0028-0836 1476-4687}, url={http://dx.doi.org/10.1038/nature24471}, DOI={10.1038/nature24471}, abstractNote={The astronomical event GW170817, detected in gravitational and electromagnetic waves, is used to determine the expansion rate of the Universe, which is consistent with and independent of existing measurements. The gravitational-wave signature of merging black holes or neutron stars yields the distance to the merger. If a counterpart is observed and its recession velocity arising from the Hubble flow is known, then a calibration of the Hubble constant that is entirely independent of the usual 'distance ladder' is possible. The gravitational-wave event of 17 August 2017 (GW170817) corresponded to the merger of two neutron stars, and an associated 'kilonova' was seen. Daniel Holz and the LIGO–Virgo collaboration, along with a group of astronomers involved with the search for the counterpart, have determined that the Hubble constant calculated this way is about 70 kilometres per second per megaparsec. This is consistent with other determinations, but independent of them. On 17 August 2017, the Advanced LIGO1 and Virgo2 detectors observed the gravitational-wave event GW170817—a strong signal from the merger of a binary neutron-star system3. Less than two seconds after the merger, a γ-ray burst (GRB 170817A) was detected within a region of the sky consistent with the LIGO–Virgo-derived location of the gravitational-wave source4,5,6. This sky region was subsequently observed by optical astronomy facilities7, resulting in the identification8,9,10,11,12,13 of an optical transient signal within about ten arcseconds of the galaxy NGC 4993. This detection of GW170817 in both gravitational waves and electromagnetic waves represents the first ‘multi-messenger’ astronomical observation. Such observations enable GW170817 to be used as a ‘standard siren’14,15,16,17,18 (meaning that the absolute distance to the source can be determined directly from the gravitational-wave measurements) to measure the Hubble constant. This quantity represents the local expansion rate of the Universe, sets the overall scale of the Universe and is of fundamental importance to cosmology. Here we report a measurement of the Hubble constant that combines the distance to the source inferred purely from the gravitational-wave signal with the recession velocity inferred from measurements of the redshift using the electromagnetic data. In contrast to previous measurements, ours does not require the use of a cosmic ‘distance ladder’19: the gravitational-wave analysis can be used to estimate the luminosity distance out to cosmological scales directly, without the use of intermediate astronomical distance measurements. We determine the Hubble constant to be about 70 kilometres per second per megaparsec. This value is consistent with existing measurements20,21, while being completely independent of them. Additional standard siren measurements from future gravitational-wave sources will enable the Hubble constant to be constrained to high precision.}, number={7678}, journal={Nature}, publisher={Springer Science and Business Media LLC}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2017}, month={Oct}, pages={85–88} }
 @article{abernathy_harry_newport_fair_kinley-hanlon_hickey_jiffar_gretarsson_penn_bassiri_et al._2018, title={Bulk and shear mechanical loss of titania-doped tantala}, volume={382}, ISSN={0375-9601}, url={http://dx.doi.org/10.1016/j.physleta.2017.08.007}, DOI={10.1016/j.physleta.2017.08.007}, abstractNote={We report on the mechanical loss from bulk and shear stresses in thin film, ion beam deposited, titania-doped tantala. The numerical values of these mechanical losses are necessary to fully calculate the Brownian thermal noise in precision optical cavities, including interferometric gravitational wave detectors like LIGO. We found the values from measuring the normal mode mechanical quality factors, Q's, in the frequency range of about 2000-10,000 Hz, of silica disks coated with titania-doped tantala coupled with calculating the elastic energy in shear and bulk stresses in the coating using a finite element model. We fit the results to both a frequency independent and frequency dependent model and find ϕshear=(8.3±1.1)×10−4, ϕbulk=(6.6±3.8)×10−4 with a frequency independent model and ϕshear(f)=(5.0±0.7)×10−4+(5.4±1.1)×10−8f, ϕbulk(f)=(11±2.8)×10−4−(8.7±4.7)×10−8f with a frequency dependent (linear) model. The ratio of these values suggest that modest improvement in the coating thermal noise may be possible in future gravitational wave detector optics made with titania-doped tantala as the high index coating material by optimizing the coating design to take advantage of the two different mechanical loss angles.}, number={33}, journal={Physics Letters A}, publisher={Elsevier BV}, author={Abernathy, Matthew and Harry, Gregory and Newport, Jonathan and Fair, Hannah and Kinley-Hanlon, Maya and Hickey, Samuel and Jiffar, Isaac and Gretarsson, Andri and Penn, Steve and Bassiri, Riccardo and et al.}, year={2018}, month={Aug}, pages={2282–2288} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2017, title={Estimating the Contribution of Dynamical Ejecta in the Kilonova Associated with GW170817}, volume={850}, ISSN={2041-8205 2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/aa9478}, DOI={10.3847/2041-8213/aa9478}, abstractNote={Abstract The source of the gravitational-wave (GW) signal GW170817, very likely a binary neutron star merger, was also observed electromagnetically, providing the first multi-messenger observations of this type. The two-week-long electromagnetic (EM) counterpart had a signature indicative of an r -process-induced optical transient known as a kilonova. This Letter examines how the mass of the dynamical ejecta can be estimated without a direct electromagnetic observation of the kilonova, using GW measurements and a phenomenological model calibrated to numerical simulations of mergers with dynamical ejecta. Specifically, we apply the model to the binary masses inferred from the GW measurements, and use the resulting mass of the dynamical ejecta to estimate its contribution (without the effects of wind ejecta) to the corresponding kilonova light curves from various models. The distributions of dynamical ejecta mass range between <?CDATA ${M}_{\mathrm{ej}}={10}^{-3}-{10}^{-2}\,{M}_{\odot }$?> for various equations of state, assuming that the neutron stars are rotating slowly. In addition, we use our estimates of the dynamical ejecta mass and the neutron star merger rates inferred from GW170817 to constrain the contribution of events like this to the r -process element abundance in the Galaxy when ejecta mass from post-merger winds is neglected. We find that if ≳10% of the matter dynamically ejected from binary neutron star (BNS) mergers is converted to r -process elements, GW170817-like BNS mergers could fully account for the amount of r -process material observed in the Milky Way.}, number={2}, journal={The Astrophysical Journal Letters}, publisher={American Astronomical Society}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2017}, month={Dec}, pages={L39} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2017, title={First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data}, volume={96}, ISSN={2470-0010 2470-0029}, url={http://dx.doi.org/10.1103/PhysRevD.96.122006}, DOI={10.1103/PhysRevD.96.122006}, abstractNote={Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signal-to-noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch between the assumed and the true signal parameters. For this reason, {\it narrow-band} analyses methods have been developed, allowing a fully coherent search for gravitational waves from known pulsars over a fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of eleven pulsars using data from Advanced LIGO's first observing run. Although we have found several initial outliers, further studies show no significant evidence for the presence of a gravitational wave signal. Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of the 11 targets over the bands searched: in the case of J1813-1749 the spin-down limit has been beaten for the first time. For an additional 3 targets, the median upper limit across the search bands is below the spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried out so far.}, number={12}, journal={Physical Review D}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2017}, month={Dec} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2017, title={GW170608: Observation of a 19 Solar-mass Binary Black Hole Coalescence}, volume={851}, ISSN={2041-8205 2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/aa9f0c}, DOI={10.3847/2041-8213/aa9f0c}, abstractNote={Abstract On 2017 June 8 at 02:01:16.49 UTC, a gravitational-wave (GW) signal from the merger of two stellar-mass black holes was observed by the two Advanced Laser Interferometer Gravitational-Wave Observatory detectors with a network signal-to-noise ratio of 13. This system is the lightest black hole binary so far observed, with component masses of <?CDATA ${12}_{-2}^{+7}\,{M}_{\odot }$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>12</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>7</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.25em" /> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> and <?CDATA ${7}_{-2}^{+2}\,{M}_{\odot }$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.25em" /> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> (90% credible intervals). These lie in the range of measured black hole masses in low-mass X-ray binaries, thus allowing us to compare black holes detected through GWs with electromagnetic observations. The source’s luminosity distance is <?CDATA ${340}_{-140}^{+140}\,\mathrm{Mpc}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>340</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>140</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>140</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.25em" /> <mml:mi>Mpc</mml:mi> </mml:math> , corresponding to redshift <?CDATA ${0.07}_{-0.03}^{+0.03}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>0.07</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.03</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.03</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> . We verify that the signal waveform is consistent with the predictions of general relativity.}, number={2}, journal={The Astrophysical Journal Letters}, publisher={American Astronomical Society}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2017}, month={Dec}, pages={L35} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2017, title={GW170814: A Three-Detector Observation of Gravitational Waves from a Binary Black Hole Coalescence}, volume={119}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/PhysRevLett.119.141101}, DOI={10.1103/PhysRevLett.119.141101}, abstractNote={On August 14, 2017 at 10∶30:43 UTC, the Advanced Virgo detector and the two Advanced LIGO detectors coherently observed a transient gravitational-wave signal produced by the coalescence of two stellar mass black holes, with a false-alarm rate of ≲1 in 27 000 years. The signal was observed with a three-detector network matched-filter signal-to-noise ratio of 18. The inferred masses of the initial black holes are 30.5+5.7−3.0M⊙ and 25.3+2.8−4.2M⊙ (at the 90% credible level). The luminosity distance of the source is 540+130−210 Mpc, corresponding to a redshift of z=0.11+0.03−0.04. A network of three detectors improves the sky localization of the source, reducing the area of the 90% credible region from 1160 deg2 using only the two LIGO detectors to 60 deg2 using all three detectors. For the first time, we can test the nature of gravitational-wave polarizations from the antenna response of the LIGO-Virgo network, thus enabling a new class of phenomenological tests of gravity.Received 23 September 2017DOI:https://doi.org/10.1103/PhysRevLett.119.141101Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasClassical black holesExperimental studies of gravityGeneral relativityGravitational wave detectionGravitation, Cosmology & Astrophysics}, number={14}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2017}, month={Oct} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2017, title={GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral}, volume={119}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/PhysRevLett.119.161101}, DOI={10.1103/PhysRevLett.119.161101}, abstractNote={On August 17, 2017 at 12∶41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave detectors made their first observation of a binary neutron star inspiral. The signal, GW170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per 8.0×10^{4} years. We infer the component masses of the binary to be between 0.86 and 2.26 M_{⊙}, in agreement with masses of known neutron stars. Restricting the component spins to the range inferred in binary neutron stars, we find the component masses to be in the range 1.17-1.60 M_{⊙}, with the total mass of the system 2.74_{-0.01}^{+0.04}M_{⊙}. The source was localized within a sky region of 28 deg^{2} (90% probability) and had a luminosity distance of 40_{-14}^{+8} Mpc, the closest and most precisely localized gravitational-wave signal yet. The association with the γ-ray burst GRB 170817A, detected by Fermi-GBM 1.7 s after the coalescence, corroborates the hypothesis of a neutron star merger and provides the first direct evidence of a link between these mergers and short γ-ray bursts. Subsequent identification of transient counterparts across the electromagnetic spectrum in the same location further supports the interpretation of this event as a neutron star merger. This unprecedented joint gravitational and electromagnetic observation provides insight into astrophysics, dense matter, gravitation, and cosmology.}, number={16}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2017}, month={Oct} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2017, title={Gravitational Waves and Gamma-Rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A}, volume={848}, ISSN={2041-8205 2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/aa920c}, DOI={10.3847/2041-8213/aa920c}, abstractNote={On 2017 August 17, the gravitational-wave event GW170817 was observed by the Advanced LIGO and Virgo detectors, and the gamma-ray burst (GRB) GRB 170817A was observed independently by the Fermi Gamma-ray Burst Monitor, and the Anticoincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory. The probability of the near-simultaneous temporal and spatial observation of GRB 170817A and GW170817 occurring by chance is $5.0\times 10^{-8}$. We therefore confirm binary neutron star mergers as a progenitor of short GRBs. The association of GW170817 and GRB 170817A provides new insight into fundamental physics and the origin of short gamma-ray bursts. We use the observed time delay of $(+1.74 \pm 0.05)\,$s between GRB 170817A and GW170817 to: (i) constrain the difference between the speed of gravity and the speed of light to be between $-3\times 10^{-15}$ and $+7\times 10^{-16}$ times the speed of light, (ii) place new bounds on the violation of Lorentz invariance, (iii) present a new test of the equivalence principle by constraining the Shapiro delay between gravitational and electromagnetic radiation. We also use the time delay to constrain the size and bulk Lorentz factor of the region emitting the gamma rays. GRB 170817A is the closest short GRB with a known distance, but is between 2 and 6 orders of magnitude less energetic than other bursts with measured redshift. A new generation of gamma-ray detectors, and subthreshold searches in existing detectors, will be essential to detect similar short bursts at greater distances. Finally, we predict a joint detection rate for the Fermi Gamma-ray Burst Monitor and the Advanced LIGO and Virgo detectors of 0.1--1.4 per year during the 2018-2019 observing run and 0.3--1.7 per year at design sensitivity.}, number={2}, journal={The Astrophysical Journal Letters}, publisher={American Astronomical Society}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2017}, month={Oct}, pages={L13} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2017, title={Multi-messenger Observations of a Binary Neutron Star Merger<sup>*}, volume={848}, ISSN={2041-8205 2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/aa91c9}, DOI={10.3847/2041-8213/aa91c9}, abstractNote={On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim$1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg$^2$ at a luminosity distance of $40^{+8}_{-8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Msun. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim$40 Mpc) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over $\sim$10 days. Following early non-detections, X-ray and radio emission were discovered at the transient's position $\sim$9 and $\sim$16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. (Abridged)}, number={2}, journal={The Astrophysical Journal Letters}, publisher={American Astronomical Society}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2017}, month={Oct}, pages={L12} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2017, title={On the progenitor of binary neutron star merger GW170817}, url={http://hdl.handle.net/11573/1073229}, DOI={10.3847/2041-8213/aa93fc}, abstractNote={Abstract On 2017 August 17 the merger of two compact objects with masses consistent with two neutron stars was discovered through gravitational-wave (GW170817), gamma-ray (GRB 170817A), and optical (SSS17a/AT 2017gfo) observations. The optical source was associated with the early-type galaxy NGC 4993 at a distance of just ∼40 Mpc, consistent with the gravitational-wave measurement, and the merger was localized to be at a projected distance of ∼2 kpc away from the galaxy’s center. We use this minimal set of facts and the mass posteriors of the two neutron stars to derive the first constraints on the progenitor of GW170817 at the time of the second supernova (SN). We generate simulated progenitor populations and follow the three-dimensional kinematic evolution from binary neutron star (BNS) birth to the merger time, accounting for pre-SN galactic motion, for considerably different input distributions of the progenitor mass, pre-SN semimajor axis, and SN-kick velocity. Though not considerably tight, we find these constraints to be comparable to those for Galactic BNS progenitors. The derived constraints are very strongly influenced by the requirement of keeping the binary bound after the second SN and having the merger occur relatively close to the center of the galaxy. These constraints are insensitive to the galaxy’s star formation history, provided the stellar populations are older than 1 Gyr.}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2017} }
 @article{albert_andré_anghinolfi_ardid_aubert_aublin_avgitas_baret_barrios-martí_basa_et al._2017, title={Search for High-energy Neutrinos from Binary Neutron Star Merger GW170817 with ANTARES, IceCube, and the Pierre Auger Observatory}, volume={850}, ISSN={2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/aa9aed}, DOI={10.3847/2041-8213/aa9aed}, abstractNote={The Advanced LIGO and Advanced Virgo observatories recently discovered gravitational waves from a binary neutron star inspiral. A short gamma-ray burst (GRB) that followed the merger of this binary was also recorded by the Fermi Gamma-ray Burst Monitor (Fermi-GBM), and the Anti-Coincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), indicating particle acceleration by the source. The precise location of the event was determined by optical detections of emission following the merger. We searched for high-energy neutrinos from the merger in the GeV–EeV energy range using the Antares, IceCube, and Pierre Auger Observatories. No neutrinos directionally coincident with the source were detected within ±500 s around the merger time. Additionally, no MeV neutrino burst signal was detected coincident with the merger. We further carried out an extended search in the direction of the source for high-energy neutrinos within the 14 day period following the merger, but found no evidence of emission. We used these results to probe dissipation mechanisms in relativistic outflows driven by the binary neutron star merger. The non-detection is consistent with model predictions of short GRBs observed at a large off-axis angle.}, number={2}, journal={The Astrophysical Journal}, publisher={American Astronomical Society}, author={Albert, A. and André, M. and Anghinolfi, M. and Ardid, M. and Aubert, J.-J. and Aublin, J. and Avgitas, T. and Baret, B. and Barrios-Martí, J. and Basa, S. and et al.}, year={2017}, month={Nov}, pages={L35} }
 @article{abbott_abbott_abbott_acernese_ackley_adams_adams_addesso_adhikari_adya_et al._2017, title={Search for Post-merger Gravitational Waves from the Remnant of the Binary Neutron Star Merger GW170817}, volume={851}, ISSN={2041-8205 2041-8213}, url={http://dx.doi.org/10.3847/2041-8213/aa9a35}, DOI={10.3847/2041-8213/aa9a35}, abstractNote={Abstract The first observation of a binary neutron star (NS) coalescence by the Advanced LIGO and Advanced Virgo gravitational-wave (GW) detectors offers an unprecedented opportunity to study matter under the most extreme conditions. After such a merger, a compact remnant is left over whose nature depends primarily on the masses of the inspiraling objects and on the equation of state of nuclear matter. This could be either a black hole (BH) or an NS, with the latter being either long-lived or too massive for stability implying delayed collapse to a BH. Here, we present a search for GWs from the remnant of the binary NS merger GW170817 using data from Advanced LIGO and Advanced Virgo. We search for short- (≲1 s) and intermediate-duration (≲500 s) signals, which include GW emission from a hypermassive NS or supramassive NS, respectively. We find no signal from the post-merger remnant. Our derived strain upper limits are more than an order of magnitude larger than those predicted by most models. For short signals, our best upper limit on the root sum square of the GW strain emitted from 1–4 kHz is <?CDATA ${h}_{\mathrm{rss}}^{50 \% }=2.1\times {10}^{-22}\,{\mathrm{Hz}}^{-1/2}$?> at 50% detection efficiency. For intermediate-duration signals, our best upper limit at 50% detection efficiency is <?CDATA ${h}_{\mathrm{rss}}^{50 \% }=8.4\times {10}^{-22}\,{\mathrm{Hz}}^{-1/2}$?> for a millisecond magnetar model, and <?CDATA ${h}_{\mathrm{rss}}^{50 \% }=5.9\times {10}^{-22}\,{\mathrm{Hz}}^{-1/2}$?> for a bar-mode model. These results indicate that post-merger emission from a similar event may be detectable when advanced detectors reach design sensitivity or with next-generation detectors.}, number={1}, journal={The Astrophysical Journal Letters}, publisher={American Astronomical Society}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and Adya, V. B. and et al.}, year={2017}, month={Dec}, pages={L16} }
 @article{abbott_abbott_abbott_abernathy_acernese_ackley_adams_adams_addesso_adhikari_et al._2016, title={Prospects for Observing and Localizing Gravitational-Wave Transients with Advanced LIGO and Advanced Virgo}, volume={19}, ISSN={2367-3613 1433-8351}, url={http://dx.doi.org/10.1007/lrr-2016-1}, DOI={10.1007/lrr-2016-1}, abstractNote={We present a possible observing scenario for the Advanced LIGO and Advanced Virgo gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We determine the expected sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron-star systems, which are considered the most promising for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and 90% credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5 deg2 to 20 deg2 will require at least three detectors of sensitivity within a factor of ∼ 2 of each other and with a broad frequency bandwidth. Should the third LIGO detector be relocated to India as expected, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.}, number={1}, journal={Living Reviews in Relativity}, publisher={Springer Science and Business Media LLC}, author={Abbott, B. P. and Abbott, R. and Abbott, T. D. and Abernathy, M. R. and Acernese, F. and Ackley, K. and Adams, C. and Adams, T. and Addesso, P. and Adhikari, R. X. and et al.}, year={2016}, month={Feb} }
 @article{kinley-hanlon_fair_jiffar_newport_gitelman_harry_billingsley_penn_2016, title={The effect of time on optical coating mechanical loss and implications for LIGO-India}, url={http://dx.doi.org/10.1088/0264-9381/33/14/147001}, DOI={10.1088/0264-9381/33/14/147001}, abstractNote={We report on the persistence of mechanical loss with time of ion beam sputtered dielectric coatings made from alternating layers of Ta_2O_5 and SiO_2 deposited onto fused silica substrates. From this, we predict the coating thermal noise in gravitational wave interferometers, after the coated optics have been stored for years. We measured the modal mechanical quality factor, Q, of two coated fused silica samples in 2015. These samples also had their modal Q's measured in 2002. We conclude that storing the coated silica disks for 13 years does not change their mechanical loss and thus the storage of Advanced LIGO gravitational wave detector optics until their future installation in India will not degrade their achievable thermal noise.}, author={Kinley-Hanlon, Maya and Fair, Hannah M and Jiffar, Isaac and Newport, Jonathan and Gitelman, Louis and Harry, Gregory and Billingsley, Garilynn and Penn, Steve}, year={2016} }