26 research outputs found
The importance of precession in modelling the direction of the final spin from a black-hole merger
The prediction of the spin of the black hole resulting from the merger of a
generic black-hole binary system is of great importance to study the
cosmological evolution of supermassive black holes. Several attempts have been
recently made to model the spin via simple expressions exploiting the results
of numerical-relativity simulations. Here, I first review the derivation of a
formula, proposed in Barausse & Rezzolla, Apj 704 L40, which accurately
predicts the final spin magnitude and direction when applied to binaries with
separations of hundred or thousands of gravitational radii. This makes my
formula particularly suitable for cosmological merger-trees and N-body
simulations, which provide the spins and angular momentum of the two black
holes when their separation is of thousands of gravitational radii. More
importantly, I investigate the physical reason behind the good agreement
between my formula and numerical relativity simulations, and nail it down to
the fact that my formula takes into account the post-Newtonian precession of
the spins and angular momentum in a consistent manner.Comment: 6 pages, 2 figures. Panel added to fig 2, discussion extended to
comply with referee's comments. Version accepted for publication as
proceeding of the 8th Amaldi International Conference on Gravitational Waves,
NYC, 21-26 June 200
On the mass radiated by coalescing black-hole binaries
We derive an analytic phenomenological expression that predicts the final
mass of the black-hole remnant resulting from the merger of a generic binary
system of black holes on quasi-circular orbits. Besides recovering the correct
test-particle limit for extreme mass-ratio binaries, our formula reproduces
well the results of all the numerical-relativity simulations published so far,
both when applied at separations of a few gravitational radii, and when applied
at separations of tens of thousands of gravitational radii. These validations
make our formula a useful tool in a variety of contexts ranging from
gravitational-wave physics to cosmology. As representative examples, we first
illustrate how it can be used to decrease the phase error of the
effective-one-body waveforms during the ringdown phase. Second, we show that,
when combined with the recently computed self-force correction to the binding
energy of nonspinning black-hole binaries, it provides an estimate of the
energy emitted during the merger and ringdown. Finally, we use it to calculate
the energy radiated in gravitational waves by massive black-hole binaries as a
function of redshift, using different models for the seeds of the black-hole
population.Comment: 9 pages (emulateapj), 4 figures. Matches version in ApJ but includes
slight changes to fig 4 described in Barausse, et al ApJ 786, 76 (2014)
(doi:10.1088/0004-637X/786/1/76), see also
http://www2.iap.fr/users/barausse/erratum_mass_formula.pd
The final spin from binary black holes in quasi-circular orbits
We revisit the problem of predicting the spin magnitude and direction of the black hole (BH) resulting from the merger of two BHs with arbitrary masses and spins inspiraling in quasi-circular orbits. We do this by analyzing a catalog of 619 recent numerical-relativity simulations collected from the literature and spanning a large variety of initial conditions. By combining information from the post-Newtonian approximation, the extreme mass-ratio limit, and perturbative calculations, we improve our previously proposed phenomenological formulae for the final remnant spin. In contrast with alternative suggestions in the literature, and in analogy with our previous expressions, the new formula is a simple algebraic function of the initial system parameters and is not restricted to binaries with spins aligned/anti-aligned with the orbital angular momentum but can be employed for fully generic binaries. The accuracy of the new expression is significantly improved, especially for almost extremal progenitor spins and for small mass ratios, yielding an rms error sigma approximate to 0.002 for aligned/anti-aligned binaries and sigma = 0.006 for generic binaries. Our new formula is suitable for cosmological applications and can be employed robustly in the analysis of the gravitational waveforms from advanced interferometric detectors
Modeling Gravitational Recoil Using Numerical Relativity
We review the developments in modeling gravitational recoil from merging
black-hole binaries and introduce a new set of 20 simulations to test our
previously proposed empirical formula for the recoil. The configurations are
chosen to represent generic binaries with unequal masses and precessing spins.
Results of these simulations indicate that the recoil formula is accurate to
within a few km/s in the similar mass-ratio regime for the out-of-plane recoil.Comment: corrections to text, 11 pages, 1 figur
Seeking for toroidal event horizons from initially stationary BH configurations
We construct and evolve non-rotating vacuum initial data with a ring
singularity, based on a simple extension of the standard Brill-Lindquist
multiple black-hole initial data, and search for event horizons with spatial
slices that are toroidal when the ring radius is sufficiently large. While
evolutions of the ring singularity are not numerically feasible for large
radii, we find some evidence, based on configurations of multiple BHs arranged
in a ring, that this configuration leads to singular limit where the horizon
width has zero size, possibly indicating the presence of a naked singularity,
when the radius of the ring is sufficiently large. This is in agreement with
previous studies that have found that there is no apparent horizon surrounding
the ring singularity when the ring's radius is larger than about twice its
mass.Comment: 24 pages, 14 figure
Renormalized spin coefficients in the accumulated orbital phase for unequal mass black hole binaries
We analyze galactic black hole mergers and their emitted gravitational waves.
Such mergers have typically unequal masses with mass ratio of the order 1/10.
The emitted gravitational waves carry the inprint of spins and mass quadrupoles
of the binary components. Among these contributions, we consider here the
quasi-precessional evolution of the spins. A method of taking into account
these third post-Newtonian (3PN) effects by renormalizing (redefining) the 1.5
PN and 2PN accurate spin contributions to the accumulated orbital phase is
developed.Comment: 10 pages, to appear in Class. Quantum Grav. GWDAW13 Proceedings
Special Issue, v2: no typos conjectur
Modelling the final state from binary black-hole coalescences
Over the last few years enormous progress has been made in the numerical
description of the inspiral and merger of binary black holes. A particular
effort has gone into the modelling of the physical properties of the final
black hole, namely its spin and recoil velocity, as these quantities have
direct impact in astrophysics, cosmology and, of course, general relativity. As
numerical-relativity calculations still remain computationally very expensive
and cannot be used to investigate the complete space of possible parameters,
semi-analytic approaches have been developed and shown to reproduce with very
high precision the numerical results. I here collect and review these efforts,
pointing out the relative strengths and weaknesses, and discuss which
directions are more promising to further improve them.Comment: Submitted to CQG, LISA-7 Special Issu
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
Exploring new physics frontiers through numerical relativity
The demand to obtain answers to highly complex problems within strong-field gravity has been met with significant progress in the numerical solution of Einstein's equations - along with some spectacular results - in various setups. We review techniques for solving Einstein's equations in generic spacetimes, focusing on fully nonlinear evolutions but also on how to benchmark those results with perturbative approaches. The results address problems in high-energy physics, holography, mathematical physics, fundamental physics, astrophysics and cosmology