@article{mumpower_mclaughlin_surman_2012, title={Formation of the rare-earth peak: Gaining insight into late-time r-process dynamics}, volume={85}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.85.045801}, abstractNote={We study the formation and final structure of the rare-earth peak ($A\ensuremath{\sim}160$) of the $r$-process nucleosynthesis. Under high-entropy conditions ($Sg100{k}_{B}$), the rare-earth peak forms at late times in the $r$-process after neutron exhaustion (neutron-to-seed ratio $R=1$) as matter decays back to stability. Since rare-earth peak formation does not occur during $(n,\ensuremath{\gamma})\ensuremath{\rightleftarrows}(\ensuremath{\gamma},n)$ equilibrium it is sensitive to the strong interplay between late-time thermodynamic evolution and nuclear physics input. Depending on the conditions, the peak forms either because of the pattern of the neutron capture rates or because of the pattern of the separation energies. We analyze three nuclear data sets under different thermodynamic conditions. We find that the subtleties of each nuclear data set, including separation energies and neutron capture rates, influence not only the final shape of the peak but also when it forms. We identify the range of nuclei which are influential in rare-earth peak formation.}, number={4}, journal={PHYSICAL REVIEW C}, author={Mumpower, Matthew R. and McLaughlin, G. C. and Surman, Rebecca}, year={2012}, month={Apr} }
 @article{surman_mclaughlin_friedland_duan_2011, title={Collective oscillations and r-process nucleosynthesis}, volume={217}, ISSN={["1873-3832"]}, DOI={10.1016/j.nuclphysbps.2011.04.081}, abstractNote={Neutrinos have recently been shown to have collective phenomenon which causes them to flavor transform near the center of the supernova. These flavor transformations can potentially impact supernova nucleosynthesis, particularly for processes that occur near the core, such as the r-process. In this paper we explore the effects of collective oscillations on a supernova r-process. We find that magnitude of the effect depends senstivitely on the astrophysical conditions—in particular on the interplay between the time when nuclei begin to exist in significant numbers and the time when the collective oscillation begins. Because of this delicate balance, a more definitive understanding of the astrophysical conditions is necesssary. Here, we explore scenarios based on outflow models currently in use and discuss their implications.}, journal={NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS}, author={Surman, Rebecca and McLaughlin, Gail C. and Friedland, Alexander and Duan, Huaiyu}, year={2011}, month={Aug}, pages={121–123} }
 @article{surman_mclaughlin_sabbatino_2011, title={NUCLEOSYNTHESIS OF NICKEL-56 FROM GAMMA-RAY BURST ACCRETION DISKS}, volume={743}, ISSN={["0004-637X"]}, DOI={10.1088/0004-637x/743/2/155}, abstractNote={We examine the prospects for producing nickel-56 from black hole accretion disks, by examining a range of steady-state disk models. We focus on relatively slowly accreting disks in the range of M☉ s−1 to M☉ s−1, as are thought to be appropriate for the central engines of long-duration gamma-ray bursts. We find that significant amounts of nickel-56 are produced over a wide range of parameter space. We discuss the influence of entropy, outflow timescale, and initial disk position on mass fraction of nickel-56 which is produced. We keep careful track of the weak interactions to ensure reliable calculations of the electron fraction, and discuss the role of the neutrinos.}, number={2}, journal={ASTROPHYSICAL JOURNAL}, author={Surman, R. and McLaughlin, G. C. and Sabbatino, N.}, year={2011}, month={Dec} }
 @article{beun_mclaughlin_surman_hix_2008, title={Fission cycling in a supernova r process}, volume={77}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.77.035804}, abstractNote={Recent halo star abundance observations exhibit an important feature of consequence to the r process: the presence of a main r process between the second and third peaks that is consistent among halo stars. We explore fission cycling and steady {beta} flow as the driving mechanisms behind this feature. The presence of fission cycling during the r process can account for nucleosynthesis yields between the second and third peaks, whereas the presence of steady {beta} flow can account for consistent r-process patterns, robust under small variations in astrophysical conditions. We employ the neutrino-driven wind of the core-collapse supernova to examine fission cycling and steady {beta} flow in the r process. As the traditional neutrino-driven wind model does not produce the required very neutron-rich conditions for these mechanisms, we examine changes to the neutrino physics necessary for fission cycling to occur in the neutrino-driven wind environment, and we explore under what conditions steady {beta} flow is obtained.}, number={3}, journal={PHYSICAL REVIEW C}, author={Beun, J. and McLaughlin, G. C. and Surman, R. and Hix, W. R.}, year={2008}, month={Mar} }
 @article{surman_beun_mclaughlin_kane_hix_2008, title={The role of neutrinos in r-process nucleosynthesis in supernovae and gamma-ray bursts}, volume={35}, ISSN={["1361-6471"]}, DOI={10.1088/0954-3899/35/1/014059}, abstractNote={The exact astrophysical site of the r-process is uncertain, but the likely candidates—supernovae and compact merger events—are environments with high neutrino fluxes. Here we examine the role of neutrinos in r-process nucleosynthesis under two separate scenarios. In the first, we consider the consequences of a reduction in the electron neutrino flux in a core-collapse supernova environment. We show that such a reduction results in a vigorous r-process with a robust abundance signature due to fission cycling. In the second, we examine the production of r-process nuclei in the outflows from a black hole accretion disk as thought to accompany a merger-type gamma-ray burst (GRB). We use a parameterized outflow model and find the neutrino fluxes emitted from the GRB accretion disk facilitate the synthesis of light r-process nuclei over a broad region of the parameter space explored.}, number={1}, journal={JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS}, author={Surman, R. and Beun, J. and McLaughlin, G. C. and Kane, S. and Hix, W. R.}, year={2008}, month={Jan} }
 @article{surman_mclaughlin_ruffert_janka_hix_2008, title={r-process nucleosynthesis in hot accretion disk flows from black hole-neutron star mergers}, volume={679}, DOI={10.1086/589507}, abstractNote={We consider hot accretion disk outflows from black hole-neutron star mergers in the context of the nucleosynthesis they produce. We begin with a three-dimensional numerical model of a black hole-neutron star merger and calculate the neutrino and antineutrino fluxes emitted from the resulting accretion disk. We then follow the element synthesis in material outflowing the disk along parameterized trajectories. We find that at least a weak r-process is produced, and in some cases a main r-process as well. The neutron-rich conditions required for this production of r-process nuclei stem directly from the interactions of the neutrinos emitted by the disk with the free neutrons and protons in the outflow.}, number={2}, journal={Astrophysical Journal Letters}, author={Surman, R. and McLaughlin, G. C. and Ruffert, M. and Janka, H. T. and Hix, W. R.}, year={2008}, pages={L117–120} }
 @article{mclaughlin_surman_2007, title={Supernova neutrinos: The accretion disk scenario}, volume={75}, ISSN={["1550-2368"]}, DOI={10.1103/physrevd.75.023005}, abstractNote={Neutrinos from core collapse supernovae can be emitted from a rapidly accreting disk surrounding a black hole, instead of the canonical protoneutron star. For galactic events, detector count rates are considerable and in fact can be in the thousands for Super-Kamiokande. The rate of occurrence of these accreting disks in the Galaxy is predicted to be on the order of $\ensuremath{\sim}{10}^{\ensuremath{-}5}\text{ }\text{ }{\mathrm{yr}}^{\ensuremath{-}1}$, yet there is little observational evidence to provide an upper limit on their formation rate. It would therefore be useful to discriminate between neutrinos which have been produced in a protoneutron star and those which have been produced accretion disks. In order to distinguish between the two scenarios, either the time profile of the neutrino luminosity, total energetics, or the relative fluxes of different neutrino flavors may be considered. The flavor content would clearly point to one scenario or the other.}, number={2}, journal={PHYSICAL REVIEW D}, author={McLaughlin, G. C. and Surman, R.}, year={2007}, month={Jan} }
 @article{surman_mclaughlin_hix_2006, title={Nucleosynthesis in the outflow from gamma-ray burst accretion disks}, volume={643}, ISSN={["1538-4357"]}, DOI={10.1086/501116}, abstractNote={We examine the nucleosynthesis products that are produced in the outflow from rapidly accreting disks. We find that the type of element synthesis varies dramatically with the degree of neutrino trapping in the disk and therefore the accretion rate of the disk. Disks with relatively high accretion rates such as Ṁ = 10 M☉ s-1 can produce very neutron-rich nuclei that are found in the r-process. Disks with more moderate accretion rates can produce copious amounts of nickel, as well as the light elements such as lithium and boron. Disks with lower accretion rates such as Ṁ = 1 M☉ s-1 produce large amounts of nickel, as well as some unusual nuclei such as 49Ti, 45Sc, 64Zn, and 92Mo. This wide array of potential nucleosynthesis products is due to the varying influence of electron neutrinos and antineutrinos emitted from the disk on the neutron-to-proton ratio in the outflow. We use a parameterization for the outflow and discuss our results in terms of entropy and outflow acceleration.}, number={2}, journal={ASTROPHYSICAL JOURNAL}, author={Surman, R. and McLaughlin, G. C. and Hix, W. R.}, year={2006}, month={Jun}, pages={1057–1064} }