Bulletin of the American Physical Society
2019 Fall Meeting of the APS Division of Nuclear Physics
Volume 64, Number 12
Monday–Thursday, October 14–17, 2019; Crystal City, Virginia
Session SM: Nuclear Astrophysics: Neutron Star Mergers and CEMP Stars |
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Chair: Aaron Couture, Los Alamos National Laboratory Room: Salon J |
Thursday, October 17, 2019 10:30AM - 10:42AM |
SM.00001: Uncertainties in Kilonova Heating from Nuclear Physics Inputs Kelsey Lund, Yonglin Zhu, Jennifer Barnes, Gail McLaughlin, Matthew Mumpower, Rebecca Surman The rapid neutron capture process (r-process) is one of the main mechanisms whereby elements heavier than iron are synthesized, and is responsible for the creation of the heaviest stable isotopes of the actinides. Observations of the gravitational wave event GW170817, and its optical counterpart, AT2017gfo, support neutron star mergers as an r-process production site. Efforts to accurately and reliably model yields and observational signatures from these sites require inputs from nuclear physics, which introduce potentially large uncertainties. We use nucleosynthesis modeling to evaluate the role of these inputs, including different nuclear mass models, fission decay rates, and daughter product distributions in lanthanide and actinide production. I will show that applying different nuclear physics inputs generates discrepancies in abundances of key isotopes which contribute significantly to the overall nuclear energy generation in the merger event, which is a necessary component of kilonova lightcurve modelling. [Preview Abstract] |
Thursday, October 17, 2019 10:42AM - 10:54AM |
SM.00002: ABSTRACT WITHDRAWN |
Thursday, October 17, 2019 10:54AM - 11:06AM |
SM.00003: Modeling Kilonova Light Curves from Neutron Star Mergers: Dependence on Astrophysical Conditions and Nuclear Inputs Yonglin Zhu, Jennifer Barnes, Kelsey Lund, Trevor Sprouse, Nicole Vassh, Matthew Mumpower, Gail McLaughlin, Rebecca Surman The unprecedented observations of the gravitational wave event, GW170817, and its optical counterpart, AT2017gfo, suggest neutron star mergers as a production site of the heaviest elements. In order to create accurate estimates of these signals, we require nuclear models, astrophysical models of the site, as well as models of the radioactive transfer. We evaluate and provide a comprehensive estimate of the nuclear and astrophysical uncertainties with nucleosynthesis informed kilonova light curve modeling. We find that the combined nuclear and astrophysical uncertainties have a significant contribution to the uncertainty the light curves associated with neutron stars mergers (kilonova). We evaluate the role of fission decay rates and fission daughter product distributions in nuclear energy generation and the production of the lanthanides and actinides, both key quantities for setting the overall luminosity and the timescale for the decay of the optical counterpart. [Preview Abstract] |
Thursday, October 17, 2019 11:06AM - 11:18AM |
SM.00004: Deep neural networks for real-time detection and characterization of gravitational waves from compact binaries Plamen Krastev Deep neural networks are computational models with the ability to learn from observational data and have already had spectacular success in tasks such as computer vision and natural language processing. I present a deep learning framework for real-time detection, classification and parameter estimation of gravitational waves from compact binaries, with a particular attention to systems involving neutron stars. The implications for detection and interpretation of recent and future gravitational-wave signals from neutron-star binaries, and the equation of state (EOS) of dense matter will be discussed. [Preview Abstract] |
Thursday, October 17, 2019 11:18AM - 11:30AM |
SM.00005: Hyperon Bulk Viscosity in Neutron Star Mergers Alexander Haber, Mark Alford In hyperonic matter, a phase lag between an imposed density oscillation and the beta reequilibration of the particle content, gives rise to a hyperonic bulk viscosity. Hyperonic bulk viscosity has been computed in the past for low temperatures and mostly by using a contact interaction matrix element. In neutron star mergers, much higher temperatures and densities than in an isolated star are reached. Therefore, it is necessary to reevaluate this phenomenon in the physical environment of neutron star mergers by including all possible reactions and going beyond the simple Fermi surface approximation. If bulk viscosity is sufficiently strong, it can significantly dampen density oscillations and should be included in merger simulations. [Preview Abstract] |
Thursday, October 17, 2019 11:30AM - 11:42AM |
SM.00006: Connecting Nuclear Structure to Stellar Astrophysics: Neutron Skin in Tin Isotopes Jack Silano, A.P. Tonchev, N. Schunck, W. Tornow, F. Krishichayan, S. Finch, D. Little, M. Jones, R. Janssens, C. Pruitt, L. Sobotka, A. Banu, J. Vavrek, N. Tsoneva The first observation of a neutron star merger by the LIGO-Virgo collaboration in 2017 highlights the need to improve our fundamental understanding of the equation of state (EOS) of dense, neutron rich matter. The origin of heavy elements in the r-process and the structure of neutron stars are governed by the properties of neutron rich matter, for which experimental data is limited. Further analysis of this historic event and all future neutron star mergers relies on constraining the nuclear EOS with experimental observables. We propose a novel method for systematically studying the evolution of the neutron skin in stable tin isotopes, by measuring the low-energy nuclear dipole strength over the broadest possible range of neutron-to-proton ratios in a single element. Nuclear resonance fluorescence with 100\% linearly polarized photons from the High Intensity $\gamma$-ray Source facility will be used to selectively measure the E1 photoabsorption strength of $^{112}$Sn and $^{124}$Sn at excitation energies from $\sim3$ MeV up to neutron separation, where the Pygmy Dipole Resonance dominates. Progress on the measurement campaign will be presente [Preview Abstract] |
Thursday, October 17, 2019 11:42AM - 11:54AM |
SM.00007: Constraining neutron-capture reactions for the astrophysical i-process Artemis Spyrou, Caley Harris, Mallory K Smith, Sean N Liddick, Katie Childers, Rebecca Lewis, Stephanie Lyons, Alicia Palmisano, Andrea L Richard, Debra Richman, Chandana Sumithrarachchi, Magne Guttormsen, Vetle Ingeberg, Ann-Cecilie Larsen, Alex Dombos, Rebecca Kelmar, Farheen Naqvi, Paul DeYoung, Panagiotis Gastis, Christina Burbage, Eva Kasanda, Dennis Muecher, Darren Bleuel, Nicholas D Scielzo, Adriana Sweet The synthesis of heavy elements in the Universe has been one of the main open questions in Nuclear Astrophysics. Recent astronomical observations of carbon enhanced metal-poor stars (CEMP) showed a significant number of stars with abundance patterns that cannot be reproduced by the traditional neutron-capture processes (s and r). An alternative process was introduced for this purpose with intermediate neutron densities, called the i process. From the nuclear physics point of view, most nuclear properties are known experimentally, and the main uncertainty comes from neutron-capture reaction rates. This talk will focus on an experimental program taking place at the NSCL to provide indirect constraints for (n,$\gamma$) reactions using the $\beta$-Oslo method. [Preview Abstract] |
Thursday, October 17, 2019 11:54AM - 12:06PM |
SM.00008: Constraining i-process Nucleosynthesis via the Neutron-Capture Cross sections of 102,103Mo Andrea L. Richard, S. N. Liddick, A. C. Dombos, A. Spyrou, T. Baumann, K. Childers, T. Ginter, E. Kwan, R. Lewis, S. Lyons, F. Naqvi, W.-J. Ong, A. Palmisano, J. Pereira, C. Prokop, S. J. Quinn, M. K. Smith, C. S. Sumithrarachchi, A. Simon, P. A. DeYoung, J. Gombas, O. Clarkson, F. Herwig, B. P. Crider, A. Algora Recent observations and stellar evolution models suggest that an intermediate process, known as the i-process, exists between the s- and r-processes, and is necessary to explain observed abundances in the Ge-Te region. Uncertainties associated with nuclear physics inputs, especially neutron-capture cross sections limit the predictive power of i-process simulations. In this work the $\beta$-Oslo method was used to study $^{103,104}$Mo at the NSCL via the $\beta$-decay of $^{103,104}$Nb which were detected using the Summing NaI(Tl) (SuN) total absorption spectrometer. Results on the NLD, $\gamma$SF, neutron-capture cross sections of $^{102}$Mo and $^{103}$Mo, and i-process calculations from the Nucleosynthesis Grid (NuGrid) Collaboration will be presented. [Preview Abstract] |
Thursday, October 17, 2019 12:06PM - 12:18PM |
SM.00009: Indirect Study of Neutron Capture for 63Fe(n,g) Mallory Smith, Artemis Spyrou, Wei Jia Ong, Sunghoon Ahn, Alex Dombos, Sean Liddick, Fernando Montes, Farheen Naqvi, Debra Richman, Hendrick Schatz, Justin Browne, Katie Childers, Ben Crider, Chris Prokop, Eric Deleeuw, Paul de Young, Christoph Langer, Becky Lewis, Zach Meisel, Jorge Pereira, Steve Quinn, Konrad Schmidt, Ann Cecilie Larsen, Magne Guttormsen Far from stability, little is known about neutron capture. An indirect method known as the $\beta$Oslo method allows n-capture rates to be experimentally constrained for radioactive nuclei. The reaction product is populated in $\beta$decay, and the $\gamma$ strength functions ($\gamma$SFs) and nuclear level densities (NLDs) are extracted simultaneously. These are used to constrain the n-capture rate. In the FeCd region, an unexpected low-energy enhancement (LEE) in the $\gamma$-decay probability has been observed. The presence of this can have a significant influence on neutron capture rates. The LEE is expected in the neutron-rich Fe isotopes. At the NSCL, 64Fe was measured with the Summing NaI detector. Recent results will be presented with a focus on the presence of the LEE. [Preview Abstract] |
Thursday, October 17, 2019 12:18PM - 12:30PM |
SM.00010: Analysis of Astrophysical Reaction Rates Using ENDF/B-VIII.0 and TENDL-2015 Libraries in 0.01-10 GK Range of Temperatures Boris Pritychenko Recent observations of neutron stars merger (GW170817) renewed interest in stellar nucleosynthesis calculations. Stellar nucleosynthesis modeling requires fully traceable, unbiased, high fidelity nuclear data. The Evaluated Nuclear Data File (ENDF) libraries contain complete collections of reaction data sets over the nuclear industry standard 10$^{-5}$ eV - 20 MeV energy span. For the first time (n,$\gamma$), (n,fission), (n,p), and (n,$\alpha$) astrophysical reaction rates were computed within 0.01-10 GK range of temperatures using ENDF/B-VIII.0 and TENDL-2015 libraries, and REACLIB fit parameters were deduced. The present results were used to estimate the slow neutron capture timescale for multiple libraries. These findings demonstrate the potential astrophysical applications of the ENDF libraries and the complementary relations between the nuclear industry and astrophysics data developments. [Preview Abstract] |
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