Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session S14: Neutron Star Structure and MergersRecordings Available
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Sponsoring Units: DAP DGRAV Chair: David Radice, Pennsylvania State University Room: Soho |
Monday, April 11, 2022 1:30PM - 1:42PM |
S14.00001: The relative contribution to heavy metals production from binary neutron star mergers and neutron star-black hole mergers Hsin-Yu Chen, Salvatore Vitale, Francois V Foucart The origin of the heavy elements in the Universe is not fully determined. Neutron star-black hole (NSBH) and \rv{binary neutron star} (BNS) mergers may both produce heavy elements via rapid neutron-capture (r-process). We use the recent detection of gravitational waves from NSBHs, improved measurements of the neutron star equation-of-state, and the most modern numerical simulations of ejected material from binary collisions to measure the relative contribution of NSBHs and BNSs to the production of heavy elements. As the amount of r-process ejecta depends on the mass and spin distribution of the compact objects, as well as on the equation-of-state of the neutron stars, we consider various models for these quantities, informed by gravitational-wave and pulsar data. We find that in most scenarios, BNSs have produced more r-process elements than NSBHs over the last 2.5 billion years. For NSBH to produce large fraction of r-process elements, black holes in NSBHs must have small masses and large aligned spins, which is disfavored by current data. |
Monday, April 11, 2022 1:42PM - 1:54PM |
S14.00002: Constraints on binary neutron star ejecta mass using NR simulations and GW170817 equations of state Amelia M Henkel, Francois V Foucart
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Monday, April 11, 2022 1:54PM - 2:06PM |
S14.00003: Binary neutron star merger simulations with the GRMHD code Spritz Jay Vijay V Kalinani, Riccardo Ciolfi, Bruno Giacomazzo, Wolfgang Kastaun, Federico Cipolletta, Lorenzo Ennoggi, Beatrice Giudici, Edoardo Giangrandi, Lorenzo Sala In the new era of multi-messenger astrophysics, events such as binary neutron star mergers have come under the limelight in the astrophysics community. In order to probe the various physical mechanisms involved in such events, it is necessary to model these systems as accurately as possible and general relativistic magnetohydrodynamic (GRMHD) simulations play a fundamental role. In this talk, I will present our new GRMHD code called Spritz, discussing its salient features including the support for realistic microphysical equations of state, the implemented neutrino leakage scheme, the inclusion of higher order methods, as well as our new conservative-to-primitive variable recovery scheme. Then, I will discuss the on-going work and some of the results obtained with this new code in the context of BNS merger simulations. |
Monday, April 11, 2022 2:06PM - 2:18PM |
S14.00004: Numerical relativity simulations of prompt collapse mergers: threshold mass and phenomenological constraints on neutron star properties after GW170817 Rahul Kashyap, Abhishek Das, David Radice, Surendra Padamata, Aviral Prakash, Domenico Logoteta, Albino Perego, Daniel Godzieba, Sebastiano Bernuzzi, Ignazio Bombaci, Farrukh J Fattoyev, Andre Schneider Binary neutron star (BNS) mergers are one of the most violent events in our universe and one of the most important sources in current and future gravitational wave (GW) observatories. There is widespread understanding that mergers result in either a black hole following a prompt collapse or, a differentially rotating massive neutron star. |
Monday, April 11, 2022 2:18PM - 2:30PM |
S14.00005: Postmerger gravitational waves as a probe of a crossover QCD transition in binary neutron star mergers Grant J Mathews, Atul Kedia, In-Saeng J Suh, Hee Il Kim Very high nuclear densities are attained in the core as neutron stars merge. During the collapse of the binary to form a black hole, it inevitably must pass through the transition from hadronic matter to a quark matter. Hence, gravitational waves emitted during this transition could be used to probe this phase of matter. In this talk, we analyze the evolution and gravitational wave emission from binary neutron star mergers using various parameterizations of the Quark-Hadron Crossover (QHC19) equation of state which is motivated by non-perturbative QCD. We observe that if a crossover or weakly first-order transition occurs the postmerger gravitational wave emission is very sensitive to the high density quark-matter equation of state and can be used to probe properties of matter in the non-perturbative regime of QCD. |
Monday, April 11, 2022 2:30PM - 2:42PM |
S14.00006: Precessing black hole - neutron star binary systems Alireza Rashti, Bernd Brugmann, Francesco Maria Fabbri, Swami Vivekanandji Chaurasia, Tim Dietrich, Maximiliano Ujevic, Wolfgang H Tichy |
Monday, April 11, 2022 2:42PM - 2:54PM |
S14.00007: I-Love-Q for proto-neutron stars Victor Santos Guedes, Kent Yagi, Cecilia Chirenti We study some universal relations (or relations that are independent of the equation of state) for proto-neutron stars in the post-bounce phase of core-collapse supernovae. Using results from three-dimensional core-collapse supernova simulations, we extract the equation of state of the system and calculate the structure of spherically symmetric proto-neutron stars. We then solve the equations that describe the gravitational field of perturbed proto-neutron stars: in the slow rotation approximation, we calculate the moment of inertia ($I$) and the spin-induced quadrupole moment ($Q$); in the small tidal deformation approximation, we calculate the tidal deformability ($\Lambda$, which is related to the tidal Love number). There are known universal relations among the I-Love-Q trio for cold neutron stars. We verify that the relations remain universal for proto-neutron stars in their late evolutionary stage and report how they connect to those for cold neutron stars. We also solve the axial gravitational perturbation equation in order to calculate the oscillation frequency and the damping time (or the real and imaginary parts of the complex frequency) of the fundamental axial $w$-mode for proto-neutron stars. We discuss the universality between such oscillation frequencies and I-Love-Q for proto-neutron stars. |
Monday, April 11, 2022 2:54PM - 3:06PM |
S14.00008: Universal Relations for Neutron Star f-mode and g-mode Oscillations Tianqi Zhao, James M Lattimer Among the various asteroseismology oscillation modes, f- and g- modes are most likely to be ultimately observed in BNS mergers, due to the relatively large coupling and shared frequencies with tidal excitations. However, the f-mode correlates strongly with static NS properties (known as I-love-Q-f relations) even for hybrid NS and QS. Nevertheless, observations of the g-mode could give us information not only about the composition but also a potential phase transition. The discontinuity g-mode frequency depends strongly on the transition density and the magnitude of the density discontinuity. Due to causality and maximum mass constraints, the discontinuity g-mode frequency has an upper bound of about 1.5 kHz. However, if the squared sound speed ratio in the inner core is restricted to 1/3, the discontinuity g-mode can only reach about 0.8 kHz, which is significantly lower than the f-mode frequency, 1.3-2.8 kHz. Also, the g-mode gravitational wave damping time is usually extremely long >10^4 s (10^2 s) for inner core with the squared sound speed ratio less than 1/3 (1), which is large compared with the f-mode damping time, 0.1-1 s. The compositional g-mode of realistic hadonic NS depends mostly on the lepton fraction at the center of the NS, with an upper bound of about 0.7 kHz. |
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