@article{guest_blair_borkowski_ghavamian_hendrick_long_petre_raymond_rest_sankrit_et al._2022, title={Locating the CSM Emission within the Type Ia Supernova Remnant N103B}, volume={926}, ISSN={["1538-4357"]}, DOI={10.3847/1538-4357/ac4913}, abstractNote={Abstract}, number={2}, journal={ASTROPHYSICAL JOURNAL}, author={Guest, Benson T. and Blair, William P. and Borkowski, Kazimierz J. and Ghavamian, Parviz and Hendrick, Sean P. and Long, Knox S. and Petre, Robert and Raymond, John C. and Rest, Armin and Sankrit, Ravi and et al.}, year={2022}, month={Feb} }
 @article{williams_borkowski_reynolds_raymond_long_morse_blair_ghavamian_sankrit_hendrick_et al._2008, title={EJECTA, DUST, AND SYNCHROTRON RADIATION IN SNR B0540-69.3: A MORE CRAB-LIKE REMNANT THAN THE CRAB}, volume={687}, ISSN={["1538-4357"]}, DOI={10.1086/592139}, abstractNote={We present near- and mid-infrared observations of the pulsar-wind nebula (PWN) SNR B0540–69.3 and its associated supernova remnant made with the Spitzer Space Telescope. We report detections of the PWN with all four IRAC bands, the 24 μm band of MIPS, and the Infrared Spectrograph (IRS). We find no evidence of IR emission from the X-ray/radio shell surrounding the PWN resulting from the forward shock of the supernova blast wave. The flux of the PWN itself is dominated by synchrotron emission at shorter (IRAC) wavelengths, with a warm dust component longward of 20 μm. We show that this dust continuum can be explained by a small amount [~(1–3) × 10−3 M☉] of dust at a temperature of ~50-65 K, heated by the shock wave generated by the PWN being driven into the inner edge of the ejecta. This is evidently dust synthesized in the supernova. We also report the detection of several lines in the spectrum of the PWN and present kinematic information about the PWN as determined from these lines. Kinematics are consistent with previous optical studies of this object. Line strengths are also broadly consistent with what one expects from optical line strengths. We find that lines arise from slow (~20 km s−1) shocks driven into oxygen-rich clumps in the shell swept up by an iron-nickel bubble, which have a density contrast of ~100-200 relative to the bulk of the ejecta, and that faster shocks (~250 km s−1) in the hydrogen envelope are required to heat dust grains to observed temperatures. We infer from estimates of heavy-element ejecta abundances that the progenitor star was likely in the range of 20-25 M☉.}, number={2}, journal={ASTROPHYSICAL JOURNAL}, author={Williams, Brian J. and Borkowski, Kazimierz J. and Reynolds, Stephen P. and Raymond, John C. and Long, Knox S. and Morse, Jon and Blair, William P. and Ghavamian, Parviz and Sankrit, Ravi and Hendrick, Sean P. and et al.}, year={2008}, month={Nov}, pages={1054–1069} }
 @article{borkowski_hendrick_reynolds_2007, title={X-ray-emitting ejecta of supernova remnant N132D}, volume={671}, ISSN={["2041-8213"]}, DOI={10.1086/524733}, abstractNote={The brightest supernova remnant in the Magellanic Clouds, N132D, belongs to the rare class of oxygen-rich remnants, about a dozen objects that show optical emission from pure heavy-element ejecta. They originate in explosions of massive stars that produce large amounts of O, although only a tiny fraction of that O is found to emit at optical wavelengths. We report the detection of substantial amounts of O at X-ray wavelengths in a recent 100 ks Chandra ACIS observation of N132D. A comparison between subarcsecond-resolution Chandra and Hubble images reveals a good match between clumpy X-ray and optically emitting ejecta on large (but not small) scales. Ejecta spectra are dominated by strong lines of He- and H-like O; they exhibit substantial spatial variations partially caused by patchy absorption within the LMC. Because optical ejecta are concentrated in a 5 pc radius elliptical expanding shell, the detected ejecta X-ray emission also originates in this shell.}, number={1}, journal={ASTROPHYSICAL JOURNAL LETTERS}, author={Borkowski, Kazimierz J. and Hendrick, Sean P. and Reynolds, Stephen P.}, year={2007}, month={Dec}, pages={L45–L48} }
 @article{borkowski_hendrick_reynolds_2006, title={Dense, Fe-rich ejecta in supernova remnants DEM L238 and DEM L249: A new class of type Ia supernova?}, volume={652}, ISSN={["1538-4357"]}, DOI={10.1086/508335}, abstractNote={We present observations of two LMC supernova remnants (SNRs), DEM L238 and DEM L249, with the Chandra and XMM-Newton X-ray satellites. Bright central emission, surrounded by a faint shell, is present in both remnants. The central emission has an entirely thermal spectrum dominated by strong Fe L-shell lines, with the deduced Fe abundance in excess of solar and not consistent with the LMC abundance. This Fe overabundance leads to the conclusion that DEM L238 and DEM L249 are remnants of thermonuclear (Type Ia) explosions. The shell emission originates in gas swept up and heated by the blast wave. A standard Sedov analysis implies about 50 M☉ in both swept-up shells, SNR ages between 10,000 and 15,000 yr, low (≲0.05 cm-3) preshock densities, and subluminous explosions with energies of 3 × 1050 ergs. The central Fe-rich supernova ejecta are close to collisional ionization equilibrium. Their presence is unexpected, because standard Type Ia SNR models predict faint ejecta emission with short ionization ages. Both SNRs belong to a previously unrecognized class of Type Ia SNRs characterized by bright interior emission. Denser than expected ejecta and/or a dense circumstellar medium around the progenitors are required to explain the presence of Fe-rich ejecta in these SNRs. Substantial amounts of circumstellar gas are more likely to be present in explosions of more massive Type Ia progenitors. DEM L238, DEM L249, and similar SNRs could be remnants of "prompt" Type Ia explosions with young (~100 Myr old) progenitors.}, number={2}, journal={ASTROPHYSICAL JOURNAL}, author={Borkowski, Kazimierz J. and Hendrick, Sean P. and Reynolds, Stephen P.}, year={2006}, month={Dec}, pages={1259–1267} }
 @article{gaensler_hendrick_reynolds_borkowski_2003, title={Discovery of a new pulsar wind nebula in the Large Magellanic Cloud}, volume={594}, ISSN={["0004-637X"]}, DOI={10.1086/378687}, abstractNote={We present new high-resolution radio and X-ray observations of the supernova remnant (SNR) B0453-685 in the Large Magellanic Cloud, carried out with the Australia Telescope Compact Array and the Chandra X-Ray Observatory, respectively. Embedded in the SNR shell is a compact central nebula producing both flat-spectrum polarized radio emission and nonthermal X-rays; we identify this source as a pulsar wind nebula (PWN) powered by an unseen central neutron star. We present a new approach by which the properties of a SNR and PWN can be used to infer upper limits on the initial spin period and surface magnetic field of the unseen pulsar, and we conclude that this star was an initial rapid rotator with current properties similar to those of the Vela pulsar. As is the case for other similarly aged sources, there is currently an interaction taking place between the PWN and the SNR's reverse shock.}, number={2}, journal={ASTROPHYSICAL JOURNAL}, author={Gaensler, BM and Hendrick, SP and Reynolds, SP and Borkowski, KJ}, year={2003}, month={Sep}, pages={L111–L114} }
 @article{hendrick_borkowski_reynolds_2003, title={Ejecta detection in middle-aged large magellanic cloud supernova remnants 0548-70.4 and 0534-69.9}, volume={593}, ISSN={["0004-637X"]}, DOI={10.1086/376356}, abstractNote={We have observed supernova remnants 0548-70.4 and 0534-69.9 in the Large Magellanic Cloud (LMC) with the Chandra X-Ray Observatory and report on the X-ray spectral analysis. Our images of 0548-70.4 and 0534-69.9 show bright central regions as well as brightened limbs. The X-ray spectra from the central regions exhibit enhanced metal abundances, in significant contrast to limb spectra, which show abundances consistent with the LMC interstellar medium (ISM). Considering the relatively old ages (~10,000 yr), these supernova remnants might be assumed to be in the Sedov phase, in which the X-ray spectra would be dominated by swept-up ISM material. The detection of high abundances in these old remnants is therefore surprising. Spectra from the limb regions were analyzed with Sedov models. The results were then used to account for blast wave emission seen in projection toward the central region and were added to a plane-parallel shock model for the reverse shock in the ejecta. We find elevated levels of iron, oxygen, magnesium, silicon, and sulfur in the bright central regions of each remnant. We introduce a new X-ray spectral shock model appropriate for heavy-element-dominated plasmas, in which electrons liberated by successive ionizations dominate the electron pool and modify the electron temperature profile. With this model, we find reverse-shock speeds of 420 km s-1 for 0548-70.4, 500 km s-1 for the northeast central region of 0534-69.9, and 360 km s-1 for its south central region. The elemental abundances favor a Type Ia supernova origin for both 0548-70.4 and 0534-69.9.}, number={1}, journal={ASTROPHYSICAL JOURNAL}, author={Hendrick, SP and Borkowski, KJ and Reynolds, SP}, year={2003}, month={Aug}, pages={370–376} }