Bulletin of the American Physical Society
APS April Meeting 2016
Volume 61, Number 6
Saturday–Tuesday, April 16–19, 2016; Salt Lake City, Utah
Session C14: Binary Neutron Star Mergers and Multi-Messenger Signals |
Hide Abstracts |
Sponsoring Units: GGR Chair: Joey Key, University of Texas, Rio Grande Valley Room: 251AB |
Saturday, April 16, 2016 1:30PM - 1:42PM |
C14.00001: Mergers of Unequal Mass Binary Neutron Stars Steven Liebling, Matthew Anderson, Luis Lehner, David Neilsen, Carlos Palenzuela We study the merger of unequal-mass neutron stars in a quasi-circular orbit with different nuclear equations of state ranging from from soft to stiff with a neutrino cooling scheme. [Preview Abstract] |
Saturday, April 16, 2016 1:42PM - 1:54PM |
C14.00002: One-arm Spiral Instability in Hypermassive Neutron Stars Formed by Dynamical-Capture Binary Neutron Star Mergers Vasileios Paschalidis, William E. East, Frans Pretorius, Stuart L. Shapiro Using general-relativistic hydrodynamical simulations, we show that merging binary neutron stars can form hypermassive neutrons stars that undergo the one-arm spiral instability. We study the particular case of a dynamical capture merger where the stars have a small spin, as may arise in globular clusters, and focus on an equal-mass scenario where the spins are aligned with the orbital angular momentum. We find that this instability develops when post-merger fluid vortices lead to the generation of a toroidal remnant -- a configuration whose maximum density occurs in a ring around the center-of-mass -- with high vorticity along its rotation axis. The instability quickly saturates on a timescale of $\sim 10$ ms, with the $m=1$ azimuthal density multipole mode dominating over higher modes. The instability also leaves a characteristic imprint on the post-merger gravitational wave signal that could be detectable if the instability persists in long-lived remnants. [Preview Abstract] |
Saturday, April 16, 2016 1:54PM - 2:06PM |
C14.00003: Equation of state survey of black hole-neutron star mergers Wyatt Brege By varying across several realistic equations of state in the regime in which most neutron star masses are most likely to appear, we can study how important a role these EOS's play in the properties of the post-merger accretion disk in mixed binary systems. In each system considered, the black hole has a mass of $M_{\rm BH}=7\,{\rm M_\odot}$ and a spin of $a^*=0.9$, and the neutron star has a mass of 1.2 or 1.4 $M_\odot}$. The realistic EOS's chosen satisfy experimental and observational constraints, and explore a wide range of neutron star compactnesses. We will address remaining uncertainties in the NS high-density EOS's and, principally, examine differences in the dynamical ejecta and consider implications for nucleosynthesis. [Preview Abstract] |
Saturday, April 16, 2016 2:06PM - 2:18PM |
C14.00004: General Relativistic Magnetohydrodynamic Simulations of Binary Neutron Star Mergers with the APR4 Equation of State Andrea Endrizzi, Riccardo Ciolfi, Bruno Giacomazzo, Wolfgang Kastaun, Takumu Kawamura We present new results of fully general relativistic magnetohydrodynamic (GRMHD) simulations of binary neutron star (BNS) mergers performed with the Whisky code. All the models use a piecewise polytropic approximation of the APR4 equation of state (EOS) for cold matter, together with a "hybrid" part to incorporate thermal effects during the evolution. We consider both equal and unequal-mass models, with total masses such that either a supramassive NS or a black hole (BH) is formed after merger. Each model is evolved with and without a magnetic field initially confined to the stellar interior. We present the different gravitational wave (GW) signals as well as a detailed description of the matter dynamics (magnetic field evolution, ejected mass, post-merger remnant properties, disk mass). Our new simulations provide a further important step in the understanding of these GW sources and their possible connection with the engine of short gamma-ray bursts (both in the "standard" and in the "time-reversal" scenarios) and with other electromagnetic counterparts. [Preview Abstract] |
Saturday, April 16, 2016 2:18PM - 2:30PM |
C14.00005: High-Mass Magnetized Binary Neutron Star Mergers and Short Gamma-Ray Bursts Bruno Giacomazzo We present new fully general relativistic magnetohydrodynamic (GRMHD) simulations of the merger of high-mass binary neutron star (BNS) systems. We considered BNSs that produce an hypermassive neutron star that promptly collapses to a spinning black hole (BH) surrounded by a magnetized accretion disk. We investigated whether such systems may launch relativistic jets and hence power short gamma-ray bursts. We considered the effects of different equations of state, different mass ratios, and different magnetic field configurations. For all cases we present a detailed study of the matter dynamics and of the magnetic field evolution, with particular attention to its global structure and possible emission of relativistic jets. [Preview Abstract] |
Saturday, April 16, 2016 2:30PM - 2:42PM |
C14.00006: MHD simulations of NSNS mergers in full GR: the role of the initial B field on the emergence of sGRB jets I Milton Ruiz, Ryan Lang, Vasileios Paschalidis, Stuart L. Shapiro Mergers of neutron star-neutron star (NSNS) binaries are among the most promising candidates for the engines that power short gamma-ray bursts (sGRBs). The most likely sGRB model requires the presence of a highly relativistic jet. However, recent relativistic simulations of NSNS mergers have shown that it is difficult for such jets to emerge following the delayed collapse of the hypermassive neutron star (HMNS) remnant. Varying the initial NS magnetic field in an NSNS binary, we have performed magnetohydrodynamic simulations in full general relativity that explore the formation of jets from the black hole-disk system following the HMNS collapse. In this talk we focus on initial dipole magnetic fields confined to the neutron star interior. [Preview Abstract] |
Saturday, April 16, 2016 2:42PM - 2:54PM |
C14.00007: MHD simulations of NSNS mergers in full GR: the role of the initial B field on the emergence of sGRB jets II Ryan Lang, Vasileios Paschalidis, Milton Ruiz, Stuart Shapiro Mergers of neutron star-neutron star (NSNS) binaries are among the most promising candidates for the engines that power short gamma-ray bursts (sGRBs). The most likely sGRB model requires the presence of a highly relativistic jet. However, recent relativistic simulations of NSNS mergers have shown that it is difficult for such jets to emerge following the delayed collapse of the hypermassive neutron star (HMNS) remnant. Varying the initial NS magnetic field in an NSNS binary, we have performed magnetohydrodynamic simulations in full general relativity that explore the formation of jets from the black hole-disk system following the HMNS collapse. In this talk we focus on initial dipole magnetic fields which extend from the neutron star interior into the exterior. [Preview Abstract] |
Saturday, April 16, 2016 2:54PM - 3:06PM |
C14.00008: Low mass binary neutron star mergers : gravitational waves and neutrino emission Francois Foucart We present numerical simulations of low mass binary neutron star mergers ($1.2M_\odot-1.2M_\odot$) with the SpEC code for a set of three nuclear-theory based, finite temperature equations of state. The merger remnant is a massive neutron star which is either permanently stable or long-lived. We focus on the post-merger gravitational wave signal, and on neutrino-matter interactions in the merger remnant. We show that the frequency peaks of the post-merger gravitational wave signal are in good agreement with predictions obtained from simulations using a simpler treatment of gravity. We then estimate the neutrino emission of the remnant using a neutrino leakage scheme and, in one case, compare these results with a gray two-moment neutrino transport scheme. We confirm the complex geometry of the neutrino emission, also observed in previous simulations with neutrino leakage, and show explicitly the presence of important differences in the neutrino luminosity, disk composition, and outflow properties between the neutrino leakage and transport schemes. We discuss the impact of our results on our ability to measure the neutron star equation of state, and on the post-merger electromagnetic signal and r-process nucleosynthesis in neutron star mergers. [Preview Abstract] |
Saturday, April 16, 2016 3:06PM - 3:18PM |
C14.00009: Dynamical ejecta from binary neutron star mergers David Radice, Filippo Galeazzi, Jonas Lippuner, Luke Roberts, Christian Ott, Luciano Rezzolla Binary neutron star mergers can drive dynamical outflows of neutron rich material. These ejecta might be the astrophysical site of production of the r-process elements. In this talk, I will present very recent full-GR, numerical relativity, simulations of binary neutron star mergers with microphysical equation of state and a simplified treatment of neutrino radiation done with the WhiskyTHC code. I will discuss the mechanisms driving the mass ejection, the role played by neutrino cooling and heating in shaping composition and morphology of the ejecta, as well as the impact on the final yields of the r-process nucleosynthesis. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700