11 research outputs found
A template bank for gravitational waveforms from coalescing binary black holes: non-spinning binaries
Gravitational waveforms from the inspiral and ring-down stages of the binary
black hole coalescences can be modelled accurately by
approximation/perturbation techniques in general relativity. Recent progress in
numerical relativity has enabled us to model also the non-perturbative merger
phase of the binary black-hole coalescence problem. This enables us to
\emph{coherently} search for all three stages of the coalescence of
non-spinning binary black holes using a single template bank. Taking our
motivation from these results, we propose a family of template waveforms which
can model the inspiral, merger, and ring-down stages of the coalescence of
non-spinning binary black holes that follow quasi-circular inspiral. This
two-dimensional template family is explicitly parametrized by the physical
parameters of the binary. We show that the template family is not only
\emph{effectual} in detecting the signals from black hole coalescences, but
also \emph{faithful} in estimating the parameters of the binary. We compare the
sensitivity of a search (in the context of different ground-based
interferometers) using all three stages of the black hole coalescence with
other template-based searches which look for individual stages separately. We
find that the proposed search is significantly more sensitive than other
template-based searches for a substantial mass-range, potentially bringing
about remarkable improvement in the event-rate of ground-based interferometers.
As part of this work, we also prescribe a general procedure to construct
interpolated template banks using non-spinning black hole waveforms produced by
numerical relativity.Comment: A typo fixed in Eq.(B11
Phenomenological template family for black-hole coalescence waveforms
Recent progress in numerical relativity has enabled us to model the
non-perturbative merger phase of the binary black-hole coalescence problem.
Based on these results, we propose a phenomenological family of waveforms which
can model the inspiral, merger, and ring-down stages of black hole coalescence.
We also construct a template bank using this family of waveforms and discuss
its implementation in the search for signatures of gravitational waves produced
by black-hole coalescences in the data of ground-based interferometers. This
template bank might enable us to extend the present inspiral searches to
higher-mass binary black-hole systems, i.e., systems with total mass greater
than about 80 solar masses, thereby increasing the reach of the current
generation of ground-based detectors.Comment: Minor changes, Submitted to Class. Quantum Grav. (Proc. GWDAW11
Reducing orbital eccentricity in binary black hole simulations
Binary black hole simulations starting from quasi-circular (i.e., zero radial
velocity) initial data have orbits with small but non-zero orbital
eccentricities. In this paper the quasi-equilibrium initial-data method is
extended to allow non-zero radial velocities to be specified in binary black
hole initial data. New low-eccentricity initial data are obtained by adjusting
the orbital frequency and radial velocities to minimize the orbital
eccentricity, and the resulting ( orbit) evolutions are compared with
those of quasi-circular initial data. Evolutions of the quasi-circular data
clearly show eccentric orbits, with eccentricity that decays over time. The
precise decay rate depends on the definition of eccentricity; if defined in
terms of variations in the orbital frequency, the decay rate agrees well with
the prediction of Peters (1964). The gravitational waveforms, which contain
cycles in the dominant l=m=2 mode, are largely unaffected by the
eccentricity of the quasi-circular initial data. The overlap between the
dominant mode in the quasi-circular evolution and the same mode in the
low-eccentricity evolution is about 0.99.Comment: 27 pages, 9 figures; various minor clarifications; accepted to the
"New Frontiers" special issue of CQ
Characteristic extraction in numerical relativity: binary black hole merger waveforms at null infinity
The accurate modeling of gravitational radiation is a key issue for
gravitational wave astronomy. As simulation codes reach higher accuracy,
systematic errors inherent in current numerical relativity wave-extraction
methods become evident, and may lead to a wrong astrophysical interpretation of
the data. In this paper, we give a detailed description of the
Cauchy-characteristic extraction technique applied to binary black hole
inspiral and merger evolutions to obtain gravitational waveforms that are
defined unambiguously, that is, at future null infinity. By this method we
remove finite-radius approximations and the need to extrapolate data from the
near zone. Further, we demonstrate that the method is free of gauge effects and
thus is affected only by numerical error. Various consistency checks reveal
that energy and angular momentum are conserved to high precision and agree very
well with extrapolated data. In addition, we revisit the computation of the
gravitational recoil and find that finite radius extrapolation very well
approximates the result at \scri. However, the (non-convergent) systematic
differences to extrapolated data are of the same order of magnitude as the
(convergent) discretisation error of the Cauchy evolution hence highlighting
the need for correct wave-extraction.Comment: 41 pages, 8 figures, 2 tables, added references, fixed typos. Version
matches published version
Testing gravitational-wave searches with numerical relativity waveforms: Results from the first Numerical INJection Analysis (NINJA) project
The Numerical INJection Analysis (NINJA) project is a collaborative effort
between members of the numerical relativity and gravitational-wave data
analysis communities. The purpose of NINJA is to study the sensitivity of
existing gravitational-wave search algorithms using numerically generated
waveforms and to foster closer collaboration between the numerical relativity
and data analysis communities. We describe the results of the first NINJA
analysis which focused on gravitational waveforms from binary black hole
coalescence. Ten numerical relativity groups contributed numerical data which
were used to generate a set of gravitational-wave signals. These signals were
injected into a simulated data set, designed to mimic the response of the
Initial LIGO and Virgo gravitational-wave detectors. Nine groups analysed this
data using search and parameter-estimation pipelines. Matched filter
algorithms, un-modelled-burst searches and Bayesian parameter-estimation and
model-selection algorithms were applied to the data. We report the efficiency
of these search methods in detecting the numerical waveforms and measuring
their parameters. We describe preliminary comparisons between the different
search methods and suggest improvements for future NINJA analyses.Comment: 56 pages, 25 figures; various clarifications; accepted to CQ
Summary of sessions B1/B2 and B2: relativistic astrophysics and numerical relativity
The numerical relativity session at GR18 was dominated by physics results on binary black hole mergers. Several groups can now simulate these from a time when the post-Newtonian equations of motion are still applicable, through several orbits and the merger to the ringdown phase, obtaining plausible gravitational waves at infinity, and showing some evidence of convergence with resolution. The results of different groups roughly agree. This new-won confidence has been used by these groups to begin mapping out the (finite dimensional) initial data space of the problem, with a particular focus on the effect of black hole spins, and the acceleration by gravitational wave recoil to hundreds of km s?1 of the final merged black hole. Other work was presented on a variety of topics, such as evolutions with matter, extreme mass ratio inspirals and technical issues such as gauge choices