257 research outputs found
Small mass plunging into a Kerr black hole: Anatomy of the inspiral-merger-ringdown waveforms
We numerically solve the Teukolsky equation in the time domain to obtain the
gravitational-wave emission of a small mass inspiraling and plunging into the
equatorial plane of a Kerr black hole. We account for the dissipation of
orbital energy using the Teukolsky frequency-domain gravitational-wave fluxes
for circular, equatorial orbits, down to the light-ring. We consider Kerr spins
, and compute the inspiral-merger-ringdown (2,2),
(2,1), (3,3), (3,2), (4,4), and (5,5) modes. We study the large-spin regime,
and find a great simplicity in the merger waveforms, thanks to the extremely
circular character of the plunging orbits. We also quantitatively examine the
mixing of quasinormal modes during the ringdown, which induces complicated
amplitude and frequency modulations in the waveforms. Finally, we explain how
the study of small mass-ratio black-hole binaries helps extending
effective-one-body models for comparable-mass, spinning black-hole binaries to
any mass ratio and spin magnitude.Comment: 20 pages, 15 figure
Surrogate model for an aligned-spin effective one body waveform model of binary neutron star inspirals using Gaussian process regression
Fast and accurate waveform models are necessary for measuring the properties
of inspiraling binary neutron star systems such as GW170817. We present a
frequency-domain surrogate version of the aligned-spin binary neutron star
waveform model using the effective one body formalism known as SEOBNRv4T. This
model includes the quadrupolar and octopolar adiabatic and dynamical tides. The
version presented here is improved by the inclusion of the spin-induced
quadrupole moment effect, and completed by a prescription for tapering the end
of the waveform to qualitatively reproduce numerical relativity simulations.
The resulting model has 14 intrinsic parameters. We reduce its dimensionality
by using universal relations that approximate all matter effects in terms of
the leading quadrupolar tidal parameters. The implementation of the time-domain
model can take up to an hour to evaluate using a starting frequency of 20Hz,
and this is too slow for many parameter estimation codes that require
sequential waveform evaluations. We therefore construct a fast and faithful
frequency-domain surrogate of this model using Gaussian process regression. The
resulting surrogate has a maximum mismatch of for the
Advanced LIGO detector, and requires 0.13s to evaluate for a waveform with a
starting frequency of 20Hz. Finally, we perform an end-to-end test of the
surrogate with a set of parameter estimation runs, and find that the surrogate
accurately recovers the parameters of injected waveforms.Comment: 19 pages, 10 figures, submitted to PR
Enriching the Symphony of Gravitational Waves from Binary Black Holes by Tuning Higher Harmonics
For the first time, we construct an inspiral-merger-ringdown waveform model
within the effective-one-body formalism for spinning, nonprecessing binary
black holes that includes gravitational modes beyond the dominant mode, specifically . Our multipolar
waveform model incorporates recent (resummed) post-Newtonian results for the
inspiral and information from 157 numerical-relativity simulations, and 13
waveforms from black-hole perturbation theory for the (plunge-)merger and
ringdown. We quantify the improved accuracy including higher-order modes by
computing the faithfulness of the waveform model against the
numerical-relativity waveforms used to construct the model. We define the
faithfulness as the match maximized over time, phase of arrival,
gravitational-wave polarization and sky position of the waveform model, and
averaged over binary orientation, gravitational-wave polarization and sky
position of the numerical-relativity waveform. When the waveform model contains
only the mode, we find that the averaged faithfulness to
numerical-relativity waveforms containing all modes with 5 ranges
from to for binaries with total mass (using
the Advanced LIGO's design noise curve). By contrast, when the
modes are also included in the model, the
faithfulness improves to for all but four configurations in the
numerical-relativity catalog, for which the faithfulness is greater than
. Using our results, we also develop also a (stand-alone) waveform
model for the merger-ringdown signal, calibrated to numerical-relativity
waveforms, which can be used to measure multiple quasi-normal modes. The
multipolar waveform model can be extended to include spin-precession, and will
be employed in upcoming observing runs of Advanced LIGO and Virgo.Comment: 28 page
Reducing orbital eccentricity of precessing black-hole binaries
Building initial conditions for generic binary black-hole evolutions without
initial spurious eccentricity remains a challenge for numerical-relativity
simulations. This problem can be overcome by applying an eccentricity-removal
procedure which consists in evolving the binary for a couple of orbits,
estimating the eccentricity, and then correcting the initial conditions. The
presence of spins can complicate this procedure. As predicted by post-Newtonian
theory, spin-spin interactions and precession prevent the binary from moving
along an adiabatic sequence of spherical orbits, inducing oscillations in the
radial separation and in the orbital frequency. However, spin-induced
oscillations occur at approximately twice the orbital frequency, therefore they
can be distinguished from the initial spurious eccentricity, which occurs at
approximately the orbital frequency. We develop a new removal procedure based
on the derivative of the orbital frequency and find that it is successful in
reducing the eccentricity measured in the orbital frequency to less than 0.0001
when moderate spins are present. We test this new procedure using
numerical-relativity simulations of binary black holes with mass ratios 1.5 and
3, spin magnitude 0.5 and various spin orientations. The numerical simulations
exhibit spin-induced oscillations in the dynamics at approximately twice the
orbital frequency. Oscillations of similar frequency are also visible in the
gravitational-wave phase and frequency of the dominant mode.Comment: 17 pages, 11 figures, fixed typo
Numerical relativity reaching into post-Newtonian territory: a compact-object binary simulation spanning 350 gravitational-wave cycles
We present the first numerical-relativity simulation of a compact-object
binary whose gravitational waveform is long enough to cover the entire
frequency band of advanced gravitational-wave detectors, such as LIGO, Virgo
and KAGRA, for mass ratio 7 and total mass as low as . We find
that effective-one-body models, either uncalibrated or calibrated against
substantially shorter numerical-relativity waveforms at smaller mass ratios,
reproduce our new waveform remarkably well, with a negligible loss in detection
rate due to modeling error. In contrast, post-Newtonian inspiral waveforms and
existing calibrated phenomenological inspiral-merger-ringdown waveforms display
greater disagreement with our new simulation. The disagreement varies
substantially depending on the specific post-Newtonian approximant used
Inspiral-merger-ringdown waveforms of spinning, precessing black-hole binaries in the effective-one-body formalism
We describe a general procedure to generate spinning, precessing waveforms
that include inspiral, merger and ringdown stages in the effective-one-body
(EOB) approach. The procedure uses a precessing frame in which
precession-induced amplitude and phase modulations are minimized, and an
inertial frame, aligned with the spin of the final black hole, in which we
carry out the matching of the inspiral-plunge to merger-ringdown waveforms. As
a first application, we build spinning, precessing EOB waveforms for the
gravitational modes l=2 such that in the nonprecessing limit those waveforms
agree with the EOB waveforms recently calibrated to numerical-relativity
waveforms. Without recalibrating the EOB model, we then compare EOB and
post-Newtonian precessing waveforms to two numerical-relativity waveforms
produced by the Caltech-Cornell-CITA collaboration. The numerical waveforms are
strongly precessing and have 35 and 65 gravitational-wave cycles. We find a
remarkable agreement between EOB and numerical-relativity precessing waveforms
and spins' evolutions. The phase difference is ~ 0.2 rad at merger, while the
mismatches, computed using the advanced-LIGO noise spectral density, are below
2% when maximizing only on the time and phase at coalescence and on the
polarization angle.Comment: 17 pages, 10 figure
Modeling gravitational waves from compact-object binaries
The direct observation and characterization of gravitational waves from binary black-hole mergers by LIGO is a testament to the crucial role played by waveform modeling in these discoveries. I will review recent developments in the ïŹeld, discussing both numerical and analytical approaches to the problem of black-hole binaries and their gravitational-wave emission
Inspiral-merger-ringdown models for spinning black-hole binaries at the interface between analytical and numerical relativity
The long-sought direct detection of gravitational waves may only be a few years away, as a new generation of interferometric experiments of unprecedented sensitivity will start operating in 2015. These experiments will look for gravitational waves with frequencies from 10 to about 1000 Hz, thus targeting astrophysical sources such as coalescing binaries of compact objects, core collapse supernovae, and spinning neutron stars, among others. The search strategy for gravitational waves emitted by compact-object binaries consists in filtering the output of the detectors with template waveforms that describe plausible signals, as predicted by general relativity, in order to increase the signal-to-noise ratio.
In this work, we modeled these systems through the effective-one-body approach to the general-relativistic 2-body problem. This formalism rests on the idea that binary coalescence is universal across different mass ratios, from the test-particle limit to the equal-mass regime. It bridges the gap between post-Newtonian theory (valid in the slow-motion, weak-field limit) and black-hole perturbation theory (valid in the small mass-ratio limit, but not limited to slow motion). The project unfolded along two main avenues of inquiry, with the goal of developing faithful inspiral-merger-ringdown waveforms for generic spinning, stellar-mass black-hole binaries. On the one hand, we studied the motion and gravitational radiation of test masses orbiting Kerr black holes in perturbation theory, with the goal of extracting strong-field information that can be incorporated into effective-one-body models. On the other hand, we worked at the interface between analytical and numerical relativity by calibrating effective-one-body models against numerical solutions of Einstein's equations, and testing their accuracy when extrapolated to different regions of the parameter space. In the course of this project, we also studied conservative effects of the 2-body dynamics, namely the periastron advance, and devised algorithms for generating realistic initial conditions for spinning, precessing black-hole binaries.
The waveform models developed in this project will be employed in data-analysis pipelines and gravitational-wave searches of advanced LIGO and Virgo. In the near future, natural extensions of this work will be the inclusion of tidal effects in the comparable-mass regime (relevant for neutron-star/black-hole binaries), and spin precession in the test-particle limit
Prototype effective-one-body model for nonprecessing spinning inspiral-merger-ringdown waveforms
We first use five non-spinning and two mildly spinning (chi_i \simeq -0.44,
+0.44) numerical-relativity waveforms of black-hole binaries and calibrate an
effective-one-body (EOB) model for non-precessing spinning binaries, notably
its dynamics and the dominant (2,2) gravitational-wave mode. Then, we combine
the above results with recent outcomes of small-mass-ratio simulations produced
by the Teukolsky equation and build a prototype EOB model for detection
purposes, which is capable of generating inspiral-merger-ringdown waveforms for
non-precessing spinning black-hole binaries with any mass ratio and individual
black-hole spins -1 \leq chi_i \lesssim 0.7. We compare the prototype EOB model
to two equal-mass highly spinning numerical-relativity waveforms of black holes
with spins chi_i = -0.95, +0.97, which were not available at the time the EOB
model was calibrated. In the case of Advanced LIGO we find that the mismatch
between prototype-EOB and numerical-relativity waveforms is always smaller than
0.003 for total mass 20-200 M_\odot, the mismatch being computed by maximizing
only over the initial phase and time. To successfully generate merger waveforms
for individual black-hole spins chi_i \gtrsim 0.7, the prototype-EOB model
needs to be improved by (i) better modeling the plunge dynamics and (ii)
including higher-order PN spin terms in the gravitational-wave modes and
radiation-reaction force.Comment: 20 pages, 8 figures. Minor changes to match version accepted for
publication in PR
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