9 research outputs found
The coalescence remnant of spinning binary black holes
We compute the gravitational radiation generated in the evolution of a family
of close binary black hole configurations, using a combination of numerical and
perturbative approximation methods. We evolve the binaries with spins, ,
aligned or counter-aligned with the orbital angular momentum from near the
innermost stable circular orbit (ISCO) down to the final single rotating black
hole. For the moderately spinning holes studied here the remnant Kerr black
hole formed at the end of an inspiral process have a rotation parameter
, suggesting it is difficult (though not excluded)
to end up with near maximally rotating holes from such scenarios.Comment: 4 pages, 5 figure
Plunge waveforms from inspiralling binary black holes
We study the coalescence of non-spinning binary black holes from near the
innermost stable circular orbit down to the final single rotating black hole.
We use a technique that combines the full numerical approach to solve Einstein
equations, applied in the truly non-linear regime, and linearized perturbation
theory around the final distorted single black hole at later times. We compute
the plunge waveforms which present a non negligible signal lasting for showing early non-linear ringing, and we obtain estimates for the total
gravitational energy and angular momentum radiated.Comment: Corrected typos in the radiated ang momentum and frequenc
Comparisons of binary black hole merger waveforms
This a particularly exciting time for gravitational wave physics.
Ground-based gravitational wave detectors are now operating at a sensitivity
such that gravitational radiation may soon be directly detected, and recently
several groups have independently made significant breakthroughs that have
finally enabled numerical relativists to solve the Einstein field equations for
coalescing black-hole binaries, a key source of gravitational radiation. The
numerical relativity community is now in the position to begin providing
simulated merger waveforms for use by the data analysis community, and it is
therefore very important that we provide ways to validate the results produced
by various numerical approaches. Here, we present a simple comparison of the
waveforms produced by two very different, but equally successful
approaches--the generalized harmonic gauge and the moving puncture methods. We
compare waveforms of equal-mass black hole mergers with minimal or vanishing
spins. The results show exceptional agreement for the final burst of radiation,
with some differences attributable to small spins on the black holes in one
case.Comment: Revtex 4, 5 pages. Published versio
Modeling gravitational radiation from coalescing binary black holes
With the goal of bringing theory, particularly numerical relativity, to bear
on an astrophysical problem of critical interest to gravitational wave
observers we introduce a model for coalescence radiation from binary black hole
systems. We build our model using the "Lazarus approach", a technique that
bridges far and close limit approaches with full numerical relativity to solve
Einstein equations applied in the truly nonlinear dynamical regime. We
specifically study the post-orbital radiation from a system of equal-mass
non-spinning black holes, deriving waveforms which indicate strongly circularly
polarized radiation of roughly 3% of the system's total energy and 12% of its
total angular momentum in just a few cycles. Supporting this result we first
establish the reliability of the late-time part of our model, including the
numerical relativity and close-limit components, with a thorough study of
waveforms from a sequence of black hole configurations varying from previously
treated head-on collisions to representative target for ``ISCO'' data
corresponding to the end of the inspiral period. We then complete our model
with a simple treatment for the early part of the spacetime based on a standard
family of initial data for binary black holes in circular orbit. A detailed
analysis shows strong robustness in the results as the initial separation of
the black holes is increased from 5.0 to 7.8M supporting our waveforms as a
suitable basic description of the astrophysical radiation from this system.
Finally, a simple fitting of the plunge waveforms is introduced as a first
attempt to facilitate the task of analyzing data from gravitational wave
detectors.Comment: 23 pages, 36 figures, RevTeX
Are moving punctures equivalent to moving black holes?
When simulating the inspiral and coalescence of a binary black-hole system,
special care needs to be taken in handling the singularities. Two main
techniques are used in numerical-relativity simulations: A first and more
traditional one ``excises'' a spatial neighbourhood of the singularity from the
numerical grid on each spacelike hypersurface. A second and more recent one,
instead, begins with a ``puncture'' solution and then evolves the full
3-metric, including the singular point. In the continuum limit, excision is
justified by the light-cone structure of the Einstein equations and, in
practice, can give accurate numerical solutions when suitable discretizations
are used. However, because the field variables are non-differentiable at the
puncture, there is no proof that the moving-punctures technique is correct,
particularly in the discrete case. To investigate this question we use both
techniques to evolve a binary system of equal-mass non-spinning black holes. We
compare the evolution of two curvature 4-scalars with proper time along the
invariantly-defined worldline midway between the two black holes, using
Richardson extrapolation to reduce the influence of finite-difference
truncation errors. We find that the excision and moving-punctures evolutions
produce the same invariants along that worldline, and thus the same spacetimes
throughout that worldline's causal past. This provides convincing evidence that
moving-punctures are indeed equivalent to moving black holes.Comment: 4 pages, 3 eps color figures; v2 = major revisions to introduction &
conclusions based on referee comments, but no change in analysis or result
The Current Status of Binary Black Hole Simulations in Numerical Relativity
Since the breakthroughs in 2005 which have led to long term stable solutions
of the binary black hole problem in numerical relativity, much progress has
been made. I present here a short summary of the state of the field, including
the capabilities of numerical relativity codes, recent physical results
obtained from simulations, and improvements to the methods used to evolve and
analyse binary black hole spacetimes.Comment: 14 pages; minor changes and corrections in response to referee
Intermediate and extreme mass-ratio inspirals — astrophysics, science applications and detection using LISA
Black hole binaries with extreme (gtrsim104:1) or intermediate (~102–104:1) mass ratios are among the most interesting gravitational wave sources that are expected to be detected by the proposed laser interferometer space antenna (LISA). These sources have the potential to tell us much about astrophysics, but are also of unique importance for testing aspects of the general theory of relativity in the strong field regime. Here we discuss these sources from the perspectives of astrophysics, data analysis and applications to testing general relativity, providing both a description of the current state of knowledge and an outline of some of the outstanding questions that still need to be addressed. This review grew out of discussions at a workshop in September 2006 hosted by the Albert Einstein Institute in Golm, Germany