Bulletin of the American Physical Society
APS April Meeting 2010
Volume 55, Number 1
Saturday–Tuesday, February 13–16, 2010; Washington, DC
Session G4: Numerical Relativity and Astrophysics |
Hide Abstracts |
Sponsoring Units: GGR DCOMP Chair: Steven Detwiler, University of Florida Room: Thurgood Marshall North |
Sunday, February 14, 2010 8:30AM - 9:06AM |
G4.00001: Statistical studies of Spinning Black-Hole Binaries Invited Speaker: We study the statistical distribution of the spins of generic black-hole binaries during the inspiral and merger, as well as the distribution of the remnant mass, spin, and recoil velocity. For the inspiral regime, we start with a random uniform distribution of spin directions $\vec{S}_1$ and $\vec{S}_2$ over the sphere and magnitudes $|\vec{S}_i/m_i^2|=0.97$ for different mass ratios. Starting from a fiducial initial separation of $r_i=50m$, we performs 3.5 post-Newtonian evolutions down to a separation of $r_f=5m$, where $m=m_1+m_2$. At this final separation, we compute the angular distribution of the spins with respect to the final orbital angular momentum. We perform $16^4$ simulations for mass ratios between $q=1$ and $q=1/16$ and compute the distribution of the angles $\hat{\vec{L}}\cdot\hat{\vec{\Delta}}$ and $\hat{\vec{L}}\cdot\hat{\vec{S}}$, directly related to recoil velocities. We find a small but statistically significant bias of the distribution towards counter-alignment of both scalar products. To study the merger of black-hole binaries, we introduce empirical formulae to describe the final remnant black hole mass, spin, and recoil velocity for merging black-hole binaries with arbitrary mass ratios and spins. Our formulae are based on the post-Newtonian scaling with amplitude parameters chosen to fit recently available fully nonlinear numerical simulations. We then evaluate these formulae for randomly chosen directions of the individual spins and magnitudes, and the binary's mass ratio. We found that the magnitude of the recoil velocity has a decaying e-folding distribution with a mean value of $2500$ km/s, and a highly peaked angular distribution along the final orbital axis. The distribution of the final black-hole spin magnitude show an universal distribution highly peaked at $S_f/m_f^2=0.73$ and with a nearly 25$^{\circ}$ degree misalignment with respect to the final orbital angular momentum, just prior to full merger of the holes. [Preview Abstract] |
Sunday, February 14, 2010 9:06AM - 9:42AM |
G4.00002: What happens when black holes and neutron stars merge? Invited Speaker: Neutron star-neutron star mergers and black hole-neutron star (BHNS) mergers are fascinating and violent events which combine strongly curved spacetimes, relativistic speeds, and supernuclear-density matter. They are also promising sources of gravitational waves and potential causes of short-duration gamma-ray bursts. The gravitational waveform and the characteristics of the post-merger accretion disk are strongly affected by the the mass ratio, the neutron star equation of state, and (for BHNS binaries) the pre-merger black hole spin. In the past few years, numerical simulations in full general relativity have made significant progress both in incorporating more realistic NS microphysics and in sampling the astrophysically relevant binary parameter space. In this talk, I review this progress, focusing particularly on studies of BHNS binaries that look at the effects of black hole spin and nuclear equation of state on the gravitational wave signal and the post-merger disk. [Preview Abstract] |
Sunday, February 14, 2010 9:42AM - 10:18AM |
G4.00003: Seeing Spacetime by Proxy: Binary Black Holes in Gaseous Environments Invited Speaker: Even though binary black hole (BBH) systems are expected to come in a wide range of masses, only the mergers of supermassive black holes---at the centers of galaxies---are expected to live in gas-rich environments. The presence of matter opens up the possibility that gravitational aspects of the binary's interaction can be transmitted---to distant observers---electromagnetically via dissipation of gas motion. Matching theoretical predictions to observations of systems before and after merger has the potential to improve our estimates of merger rates, and tell us about the spin and mass distributions of supermassive black holes. Seeing the light from the precise moment of merger---if such a robust signature exists---presents us with additional information such as more evidence that black holes merge, how material behaves in the strong-field dynamical regime of gravity, and a new and independent class of redshift-distance measurements if found with accompanying gravitational radiation (as with LISA). All of these exciting possibilities require realistic predictions for how gas---which will likely be magnetized---responds to a BBH evolution. In this talk, we will provide a brief survey of past and current work on theoretical models of BBH systems with gas. The consequences of recent numerical relativity simulations on these electromagnetic signature models will be emphasized. Knowledge gleaned from simulations of single black hole accretion disks will be presented to explain the likely importance of initial conditions on the circumbinary disk. We will also describe our efforts towards accurately simulating magnetized BBH disks just prior to merger, and a disk's response to the binary's coalescence and recoil of the nascent black hole. [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