Bulletin of the American Physical Society
2007 APS April Meeting
Volume 52, Number 3
Saturday–Tuesday, April 14–17, 2007; Jacksonville, Florida
Session B7: Binary Black Holes: Orbits, Mergers and Waveforms |
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Sponsoring Units: GGR Chair: Pedro Marronetti, Florida Atlantic University Room: Hyatt Regency Jacksonville Riverfront Grand 8 |
Saturday, April 14, 2007 10:45AM - 11:21AM |
B7.00001: Spin- orbit interactions in black-hole binaries Invited Speaker: Carlos Lousto We present the first fully-nonlinear numerical study of the dynamics of highly spinning black-hole binaries. We evolve binaries from quasicircular orbits, and find that the last stages of the orbital motion of black-hole binaries are profoundly affected by their individual spins. In order to cleanly display its effects, we consider two equal mass holes with individual spin parameters $S/m^2=0.757$, both aligned and anti-aligned with the orbital angular momentum (and compare with the spinless case), and with an initial orbital period of $125M$. We find that the aligned case completes three orbits and merges significantly after the anti-aligned case, which completes less than one orbit. The total energy radiated for the former case is $\sim$7\% while for the latter it is only $\sim$2\%. The final Kerr hole remnants have rotation parameters $a/M=0.89$ and $a/M=0.44$ respectively, showing the unlikeliness of creating a maximally rotating black hole out of the merger of two spinning holes. To calculate the transfer of angular momentum from orbital to spin, we start with two quasi-circular configurations, one with initially non-spinning black holes, the other with corotating black holes. In both cases the binaries complete almost two orbits before merging. We find that, during these last orbits, the spin-orbit coupling is far too weak to tidally lock the binary to a corotating state during the late-inspiral phase. We also use the `moving puncture' approach to perform fully non-linear evolutions of spinning quasi-circular black-hole binaries with individual spins not aligned with the orbital angular momentum. We evolve configurations with the individual spins pointing in the orbital plane and 45-degrees above the orbital plane. We introduce a technique to measure the spin direction and track the precession of the spin during the merger, as well as measure the spin flip in the remnant horizon. These simulations show for the first time how the spins are reoriented during the final stage of binary black hole mergers verifying the hypothesis of the spin-flip phenomenon. We also compute the track of the holes before merger and observe a precession of the orbital plane with frequency similar to the orbital frequency and amplitude increasing with time. [Preview Abstract] |
Saturday, April 14, 2007 11:21AM - 11:57AM |
B7.00002: Binary Black Holes: Mergers, Dynamics, and Waveforms Invited Speaker: Joan Centrella The final merger of two black holes is expected to be the strongest gravitational wave source for ground-based interferometers such as LIGO, VIRGO, and GEO600, as well as the space-based interferometer LISA. Observing these sources with gravitational wave detectors requires that we know the radiation waveforms they emit. Since these mergers take place in regions of extreme gravity, we need to solve Einstein's equations of general relativity on a computer in order to calculate these waveforms. For more than 30 years, scientists have tried to compute black hole mergers using the methods of numerical relativity. The resulting computer codes have been plagued by instabilities, causing them to crash well before the black holes in the binary could complete even a single orbit. Within the past few years, however, this situation has changed dramatically, with a series of remarkable breakthroughs. This talk will focus on new simulations that are revealing the dynamics and waveforms of binary black hole mergers, and their applications in gravitational wave detection, data analysis, and astrophysics. [Preview Abstract] |
Saturday, April 14, 2007 11:57AM - 12:33PM |
B7.00003: Binary black holes and their echoes in the Universe Invited Speaker: Pablo Laguna A new window in astronomy will open once gravitational-wave interferometers detect ``first light.'' These detectors will give us a revolutionary view of the Universe, complementary to the electromagnetic perspective. The detection and characterization of gravitational waves is a formidable undertaking, requiring innovative engineering, powerful data analysis tools as well as careful theoretical and numerical modeling. Binary black holes are expected to be one of the primary sources of gravitational radiation. I will discuss aspects of numerical simulations of binary black holes in connection with spins, gravitational recoil and eccentricities that have been recently obtained and have direct relevance to gravitational wave data analysis and astrophysics. [Preview Abstract] |
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