Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session K16: Simulations of Binary Neutron StarsRecordings Available
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Sponsoring Units: DGRAV DAP Chair: Zachariah Etienne, University of Idaho Room: 16th Floor Sky Lobby |
Sunday, April 10, 2022 1:30PM - 1:42PM |
K16.00001: Accurate, long-term binary neutron stars simulations with IllinoisGRMHD and HARM3D Leonardo Werneck We perform binary neutron star (BNS) merger simulations in full dynamical general relativity with IllinoisGRMHD, on Cartesian AMR grid. After the remnant black hole (BH) has become nearly stationary, continuing to simulate the surrounding accretion disk on Cartesian grids over long timescales (~1s) would be suboptimal, as the plasma flows obliquely across coordinate lines and numerical errors quickly sap angular momentum from the disk. To address this, we hand off the GRMHD and spacetime data from IllinoisGRMHD to HARM3D, a GRMHD code that specializes in modeling BH accretion disks in static spacetimes over long timescales on spherical-like coordinate grids. We demonstrate a smooth and reliable transition of GRMHD fields and spacetime data, enabling us to efficiently and reliably evolve BNS dynamics for the needed longer timescales. We also discuss future plans, which involve incorporating advanced equations of state and neutrino physics into BNS simulations using this approach. |
Sunday, April 10, 2022 1:42PM - 1:54PM |
K16.00002: Handing-Off the Outcome of Binary Neutron Star Mergers for Accurate and Long-Term Post-Merger Simulations Federico G Lopez Armengol, Zachariah B Etienne, Scott C Noble, Bernard J Kelly, Leonardo Werneck, Brendan Drachler, Manuela Campanelli, Federico Cipolletta, Yosef Zlochower, Ariadna Murguia-Berthier, Lorenzo Enoggi, Mark J Avara, Riccardo Ciolfi, Joshua A Faber, Fiaco Grace, Bruno Giacomazzo, Tanmayee Gupte, Trung Ha, Julian H Krolik, Vassilios Mewes, Richard O’Shaughnessy, Jesús M Rueda-Becerril, Jeremy Schnittman We present the HandOff, a set of computational tools that enables the transition of a general relativistic magnetohydrodynamic (GRMHD) simulation between two numerical codes, IllinoisGRMHD and Harm3d. While the first code evolves the equations of full dynamical General Relativity, making use of a Cartesian grid with adaptive-mesh refinement, the second code specializes in modeling black hole accretion disks in static spacetimes over long timescales, making use of general coordinate systems with spherical topology. The HandOff is particularly interesting for transitioning the outcomes of binary neutron star mergers (BNS) to a grid better suited to the geometry and requirements of the post-merger. We demonstrate that the HandOff allows for a smooth and reliable transition of GRMHD fields and spacetime data, enabling us to efficiently and reliably evolve BNS dynamics well beyond merger. |
Sunday, April 10, 2022 1:54PM - 2:06PM |
K16.00003: SphericalNR: GRMHD Simulations in Curvilinear Coordinates Yosef Zlochower Many strongly gravitating astrophysical GRMHD systems exhibit approximately cylindrical symmetry in the bulk motion of the fluid. In this talk, we describe a new code, SphericalNR, that is used to evolve such systems in curvilinear coordinates. Basing the numerical algorithms on curvilinear coordinates can provide higher accuracies, with smaller computational grids, when compared to Cartesian coordinates. In this talk, we present the challenges and successes in accurately evolving strongly gravitating systems such as unstable neutron stars and circumbinary accretion disks. |
Sunday, April 10, 2022 2:06PM - 2:18PM |
K16.00004: Numerical Simulations of Realistic Binary Neutron Stars Maria C Babiuc The new field of Multi-Messenger Astrophysics adds gravitational waves to the detection of electromagnetic signals, enabling us to gain previously unavailable insights about our Universe. It started with the detection in multiple wavelengths of the neutron star merger (GW/GRB 170817A), and proved its extraordinary potential in answering fundamental questions about the characteristics of neutron stars. The promise of MMA can be realized only with accurate theoretical models to decode the many unknown mechanisms leading to powerful electromagnetic signals such as fast radio bursts, cosmic jets, and gamma ray bursts that might be present during the merger. This work seeks to discern the role played by the magnetic field geometry and strength, equation of state and mass ratio during the chaotic dynamics of the merger, in generating or shutting off detectable multi-messenger signals from binary neutron star collisions. Specifically, we carry out numerical simulations of realistic binary neutron stars, to investigate the key factors responsible for steering the production of detectable electromagnetic counterparts to the gravitational wave signals. This work addresses also the reproducibility of results by using publicly available, open-source software and documenting the workflow, which will enable researchers and students to regenerate the same findings and produce new results. |
Sunday, April 10, 2022 2:18PM - 2:30PM |
K16.00005: Recoil Velocity of Binary Neutron Star Remnants Sumeet S Kulkarni, Anuradha Gupta, David Radice, Surendra Padamata, Rahul Kashyap The LIGO-Virgo gravitational wave detectors have observed 4 events involving neutron stars: two binary neutron star (BNS) mergers (GW170817 and GW190425), and two neutron star-black hole mergers (GW200105 and GW200115). However, our theoretical understanding of the remnant properties of such systems is incomplete due to the complexities related to the modeling of matter effects and the very high computational cost of corresponding numerical relativity simulations. An important such property is the recoil velocity, which is imparted onto the remnant due to the anisotropic emission of gravitational radiation and the dynamical ejection of matter in the post-merger kilonova. In this work, we combine gravitational radiation as well as dynamical ejecta distributions, computed by the Computational Relativity (CoRe) numerical simulations, to get accurate estimates for BNS remnant recoil velocities. Based on this, we also obtain a numerical relativity fit for recoil velocity as a function of BNS parameters. BNS remnant recoil velocities play an important role in determining if the remnant is retained by its environment for future hierarchical mergers in a dynamical formation scenario which, in turn, can populate black holes within the lower mass gap of $\sim 3-5 M_{\odot}$. |
Sunday, April 10, 2022 2:30PM - 2:42PM |
K16.00006: Probing the core of neutron stars through the binary Love relations in gravitational wave observations Hung Tan, Veronica Dexheimer, Jacquelyn Noronha-Hostler, Nicolas Yunes The binary love relations are equation-of-state-insensitive relations that have been used to break degeneracies in neutron star observations and learn more about neutron stars. As gravitational wave detectors become more sensitive, one may begin to extract information about the core of a neutron star. In this talk, I will discuss how the observation of the binary love relation may reveal some specific features in the equation of state, which imply new degrees of freedom at the core. |
Sunday, April 10, 2022 2:42PM - 2:54PM |
K16.00007: Signatures of deconfined quark phases in binary neutron star mergers Aviral Prakash, David Radice, Domenico Logoteta, Albino Perego, Vsevolod Nedora, Ignazio Bombaci, Rahul Kashyap, Sebastiano Bernuzzi, Andrea Endrizzi We investigate QCD phase transitions in the context of binary neutron star (BNS) mergers. Comparing numerical relativity simulations with equations of state (EOS) that model respectively hadronic matter and a first-order phase transition to quarks, we find that the latter causes an earlier collapse of the merger remnant to a black hole. The phase transition is imprinted on the postmerger gravitational wave (GW) signal duration, amplitude, and peak frequency and does not cause significant deviations from quasi-universal relations for the postmerger GW peak frequency. Hence the postmerger GW peak frequency alone is not sufficient to conclusively exclude or confirm the presence of a phase transition. We also study the impact of the phase transition on dynamical ejecta, remnant accretion disk masses, r-process nucleosynthetic yields, and associated electromagnetic (EM) counterparts. The most robust feature is the non-thermal afterglow caused by the interaction of the fastest component of the dynamical ejecta and the interstellar medium, which is systematically boosted in binaries with phase transition as a consequence of the more violent merger they experience. |
Sunday, April 10, 2022 2:54PM - 3:06PM |
K16.00008: Postmerger evolution of neutron star mergers as a probe of quark matter equation of state Atul Kedia, Grant J Mathews, Hee Il Kim, In-Saeng J Suh The gravitational radiation from binary neutron star mergers can effectively probe the nuclear equation of state (EOS). As neutron stars merge very high nuclear densities are attained at the core. As the binary collapses to form a black hole, it inevitably must pass through the transition from hadronic matter to a quark matter, and hence could be probed via the emitted gravitational waves. In this paper, we analyze the evolution and gravitational wave emission from binary neutron star mergers using a parameterizations of the Quark-Hadron Crossover (QHC19) EOS which is motivated by non-perturbative QCD. We observe that the postmerger gravitational wave emission is very sensitive to the high density-quark matter EOS and could be used to probe properties of matter in the non-perturbative phase of QCD. |
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