Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session Y13: Numerical Relativity: Double Neutron Stars and Black Hole Neutron Stars |
Hide Abstracts |
Sponsoring Units: GGR Chair: Serguei Ossokine, University of Toronto Room: Key 9 |
Tuesday, April 14, 2015 1:30PM - 1:42PM |
Y13.00001: New Method to Construct Initial Data for Compact Object Binaries Pablo Laguna, Michael Clark We introduce a new approach to construct initial data for binary systems with neutron star companions. The approach is a generalization of the puncture initial data for binary black holes based on Bowen-York extrinsic curvature solutions to the momentum constraint. As with the binary black holes case, the new approach allows one setting orbital configurations with input directly from post-Newtonian approximations. We demonstrate the effectiveness of this initial data method with evolutions of double neutron star and black hole-neutron star binariess in quasi-circular orbits. [Preview Abstract] |
Tuesday, April 14, 2015 1:42PM - 1:54PM |
Y13.00002: Simulations of binary neutron stars with reduced eccentricity Wolfgang Tichy, Niclas Moldenhauer, Charalampos Markakis, Nathan Johnson-McDaniel, Bernd Br\"ugmann, Tim Dietrich, Sebastiano Bernuzzi In order to construct initial data, binary neutron stars in quasi-circular orbits are usually modeled as helically symmetric, i.e., stationary in a rotating frame. This symmetry gives rise to a first integral of the Euler equation, often employed for constructing equilibrium solutions via iteration. We have extended this approach to the case of eccentric orbits by considering configurations at apoapsis that are instantaneously stationary in a rotating frame. We approximate the orbit of each star at apoapsis as an ellipse and use the ellipse's inscribed circle to construct a helical symmetry vector. In addition, we add a radial piece to the symmetry vector to model the inspiral. These modifications result in two freely specifiable parameters, an eccentricity parameter $e$ and a radial velocity parameter $v_r$. If both are set to zero one recovers standard initial data. However, when such initial data are evolved one finds that the resulting orbits show a non-negligible eccentricity. We present an iterative method that allows us to adjust the parameters $e$ and $v_r$ in such a way that the orbits that result from evolution have reduced eccentricities. [Preview Abstract] |
Tuesday, April 14, 2015 1:54PM - 2:06PM |
Y13.00003: Gravitational radiation from binary neutron star mergers: Magnetic and microphysical effects David Neilsen, Matthew Anderson, Luis Lehner, Steven L. Liebling, Patrick Motl, Carlos Palenzuela, Marcelo Ponce Binary neutron star mergers will be important sources of gravitational radiation for Advanced LIGO. Understanding how different physical processes--such as magnetic and microphysical effects due to equations of state or neutrino cooling--are imprinted on the radiation is important for learning more about these systems. We perform a series of binary neutron star mergers to examine some of these effects on the gravitational radiation. We use three different realistic equations of state, ranging from soft to stiff, initially magnetized stars, and include neutrino cooling of the post-merger system using a leakage scheme. We discuss possible observational signatures for these systems. [Preview Abstract] |
Tuesday, April 14, 2015 2:06PM - 2:18PM |
Y13.00004: Binary Neutron Stars with Arbitrary Spins in Numerical Relativity Harald Pfeiffer, Nick Tacik, Francois Foucart, Roland Haas, Jeffrey Kaplan, Curran Muhlberger, Matt Duez, Lawrence Kidder, Mark Scheel, Bela Szilagyi We present a code to construct initial data for binary neutron star where the stars are rotating. Our code, based on the formalism developed by Tichy, allows for arbitrary rotation axes of the neutron stars and is able to achieve rotation rates near rotational breakup. We demonstrate that orbital eccentricity of the binary neutron stars can be controlled to $\sim 0.1\%$. Preliminary evolutions show that spin- and orbit-precession of Neutron stars is well described by post-Newtonian approximation. The neutron stars show quasi-normal mode oscillations at an amplitude which increases with the rotation rate of the stars. [Preview Abstract] |
Tuesday, April 14, 2015 2:18PM - 2:30PM |
Y13.00005: GRMHD Simulations of Binary Neutron Star Mergers with Piecewise Polytropic Equations of State Bruno Giacomazzo We present new results of fully general relativistic magnetohydrodynamic (GRMHD) simulations of binary neutron star (BNS) mergers performed with the Whisky code. Our new simulations consider both equal and unequal-mass systems and describe the NS matter via piecewise polytropic equations of state (EOSs). BNS mergers are powerful sources of gravitational waves (GWs) that can be detected by ground based detectors, such as advanced Virgo and LIGO, and they are also thought to be behind the central engine powering short gamma-ray bursts. In our simulations we therefore focus both on the GW emission and on the dynamics of matter and magnetic fields, both in the case a black hole is promptly formed and in the case of the formation of a long-lived magnetized NS. Since the EOS has an important role in both GW emission and matter dynamics, our simulations employ piecewise polytropic EOSs composed by seven pieces, four for the low-density regions (including the crust) and three for the core, in order to more accurately match physically motivated EOSs. Thermal effects are also included in order to more properly describe the post-merger dynamics. [Preview Abstract] |
Tuesday, April 14, 2015 2:30PM - 2:42PM |
Y13.00006: Binary Neutron Star Mergers with Initial Spin Wolfgang Kastaun, Filippo Galeazzi Recently, we performed simulations of binary neutron star mergers which included both nuclear physics equations of state and stars with initial spin for the first time. The focus was on systems resulting in hyper-massive neutron stars. I will discuss the influence of realistic amounts of spin on the outcome, in particular regarding the gravitational wave signal. We also investigated the structure and dynamics of the remnant in detail, revealing some interesting new aspects. For example, we observe rotational profiles not fitting the standard notion of a rapidly rotating core, and show that strong quasi-radial oscillations in the post merger phase have an impact on the gravitational wave spectrum via a modulation of the m=2 mode frequency, offering an alternative to recent interpretations of high frequency side-peaks as non-linear combination frequencies. Finally, we discuss a possible mechanism in which the initial neutron star spins can influence the amount of ejected matter in some cases. [Preview Abstract] |
Tuesday, April 14, 2015 2:42PM - 2:54PM |
Y13.00007: Post-merger evolution of a neutron star-black hole binary with neutrino transport Francois Foucart, Evan O'Connor, Luke Roberts, Matthew Duez, Lawrence Kidder, Christian Ott, Harald Pfeiffer, Mark Scheel, Bela Szilagyi We present a first simulation of the post-merger evolution of a black hole-neutron star binary in full general relativity using an energy-integrated truncated moment formalism for neutrino transport. The moment formalism is included as a new module in the SpEC code. We describe the implementation and tests of this new module, and its use to study the formation phase of an accretion disk after a black hole-neutron star merger. We discuss differences with simpler treatments of the neutrinos, the importance of relativistic effects, and the impact of the formation phase of the disk on its expected long-term evolution. We also show that a small amount of material is ejected in the polar region during the circularization of the disk and its interactions with fallback material, and discuss its effects on potential electromagnetic counterparts to the merger. [Preview Abstract] |
Tuesday, April 14, 2015 2:54PM - 3:06PM |
Y13.00008: Accretion of the magnetized neutrino-cooled torus on a rotating black hole Fatemeh Hossein Nouri Neutrino-cooled accretion flow around a black hole, produced by a compact binary merger, is a promising scenario for a short duration gamma ray burst central engine. The turbulence caused by magneto-rotational instability is expected to play an important role in driving accretion and thermal equilibrium of the disk. We study the magnetically-driven post-merger evolution of a black hole-neutron star binary system using results from a previous simulation and Einstein's Spectral Code's MHD module. We mostly focus on studying the effects of neutrino cooling and magnetic filed on the structure of the disk and neutrino emission and neutrino-antineutrino energy deposition of the disk. [Preview Abstract] |
Tuesday, April 14, 2015 3:06PM - 3:18PM |
Y13.00009: A model for neutrino emission from nuclear accretion disks Michael Deaton Compact object mergers involving at least one neutron star can produce short-lived black hole accretion engines. Over tens to hundreds of milliseconds such an engine consumes a disk of hot, nuclear-density fluid, and drives changes to its surrounding environment through luminous emission of neutrinos. The neutrino emission may drive an ultrarelativistic jet, may peel off the disk's outer layers as a wind, may irradiate those winds or other forms of ejecta and thereby change their composition, may change the composition and thermodynamic state of the disk itself, and may oscillate in its flavor content. We present the full spatial-, angular-, and energy-dependence of the neutrino distribution function around a realistic model of a nuclear accretion disk, to inform future explorations of these types of behaviors. [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