145 research outputs found
Measuring the spin of black holes in binary systems using gravitational waves
Compact binary coalescences are the most promising sources of gravitational
waves (GWs) for ground based detectors. Binary systems containing one or two
spinning black holes are particularly interesting due to spin-orbit (and
eventual spin-spin) interactions, and the opportunity of measuring spins
directly through GW observations. In this letter we analyze simulated signals
emitted by spinning binaries with several values of masses, spins, orientation,
and signal-to-noise ratio. We find that spin magnitudes and tilt angles can be
estimated to accuracy of a few percent for neutron star--black hole systems and
5-30% for black hole binaries. In contrast, the difference in the
azimuth angles of the spins, which may be used to check if spins are locked
into resonant configurations, cannot be constrained. We observe that the best
performances are obtained when the line of sight is perpendicular to the
system's total angular momentum, and that a sudden change of behavior occurs
when a system is observed from angles such that the plane of the orbit can be
seen both from above and below during the time the signal is in band. This
study suggests that the measurement of black hole spin by means of GWs can be
as precise as what can be obtained from X-ray binaries.Comment: 4 figures, Version accepted for publication on PR
PESummary: the code agnostic Parameter Estimation Summary page builder
PESummary is a Python software package for processing and visualising data
from any parameter estimation code. The easy to use Python executable scripts
and extensive online documentation has resulted in PESummary becoming a key
component in the international gravitational-wave analysis toolkit. PESummary
has been developed to be more than just a post-processing tool with all outputs
fully self-contained. PESummary has become central to making gravitational-wave
inference analysis open and easily reproducible.Comment: 26 pages, 5 figures; resubmission following reviewers comment
Parameter estimation for heavy binary-black holes with networks of second-generation gravitational-wave detectors
The era of gravitational-wave astronomy has started with the discovery of the
binary black hole coalescences (BBH) GW150914 and GW151226 by the LIGO
instruments. These systems allowed for the first direct measurement of masses
and spins of black holes. The component masses in each of the systems have been
estimated with uncertainties of over 10\%, with only weak constraints on the
spin magnitude and orientation. In this paper we show how these uncertainties
will be typical for this type of source when using advanced detectors. Focusing
in particular on heavy BBH of masses similar to GW150914, we find that typical
uncertainties in the estimation of the source-frame component masses will be
around 40\%. We also find that for most events the magnitude of the component
spins will be estimated poorly: for only 10\% of the systems the uncertainties
in the spin magnitude of the primary (secondary) BH will be below 0.7 (0.8).
Conversely, the effective spin along the angular momentum can be estimated more
precisely than either spins, with uncertainties below 0.16 for 10\% of the
systems. We also quantify how often large or negligible primary spins can be
excluded, and how often the sign of the effective spin can be measured. We show
how the angle between the spin and the orbital angular momentum can only seldom
be measured with uncertainties below 60. We then investigate how the
measurement of spin parameters depends on the inclination angle and the total
mass of the source. We find that when precession is present, uncertainties are
smaller for systems observed close to edge-on. Contrarily to what happens for
low-mass, inspiral dominated, sources, for heavy BBH we find that large spins
aligned with the orbital angular momentum can be measured with small
uncertainty. We also show how spin uncertainties increase with the total mass.
Finally...Comment: 18 pages, 28 figures. The abstract is cut in the Arxiv metadata.
Refer to PDF. Version accepted by PR
Parameter Estimation with a spinning multi-mode waveform model: IMRPhenomHM
Gravitational waves from compact binary coalescence sources can be decomposed
into spherical-harmonic multipoles, the dominant being the quadrupole () modes. The contribution of sub-dominant modes towards total signal
power increases with increasing binary mass ratio and source inclination to the
detector. It is well-known that in these cases neglecting higher modes could
lead to measurement biases, but these have not yet been quantified with a
higher-mode model that includes spin effects. In this study, we use the
multi-mode aligned-spin phenomenological waveform model IMRPhenomHM to
investigate the effects of including multi-mode content in estimating source
parameters and contrast the results with using a quadrupole-only model
(IMRPhenomD). We use as sources IMRPhenomHM and hybrid EOB-NR waveforms over a
range of mass-ratio and inclination combinations, and recover the parameters
with IMRPhenomHM and IMRPhenomD. These allow us to quantify the accuracy of
parameter measurements using a multi-mode model, the biases incurred when using
a quadrupole-only model to recover full (multi-mode) signals, and the
systematic errors in the IMRPhenomHM model. We see that the parameters
recovered by multi-mode templates are more precise for all non-zero
inclinations as compared to quadrupole templates. For multi-mode injections,
IMRPhenomD recovers biased parameters for non-zero inclinations with lower
likelihood while IMRPhenomHM recovered parameters are accurate for most cases,
and if a bias exists, it can be explained as a combined effect of observational
priors and (in the case of hybrid-NR signals) waveform inaccuracies. For cases
where IMRPhenomHM recovers biased parameters, the bias is always smaller than
the corresponding IMRPhenomD recovery, and we conclude that IMRPhenomHM will be
sufficiently accurate to allow unbiased measurements for most GW observations.Comment: 14 pages, 7 figure
Black-hole Spectroscopy by Making Full Use of Gravitational-Wave Modeling
The Kerr nature of a compact-object-coalescence remnant can be unveiled by
observing multiple quasi-normal modes (QNMs) in the post-merger signal. Current
methods to achieve this goal rely on matching the data with a superposition of
exponentially damped sinusoids with amplitudes fitted to numerical-relativity
(NR) simulations of binary black-hole (BBH) mergers. These models presume the
ability to correctly estimate the time at which the gravitational-wave (GW)
signal starts to be dominated by the QNMs of a perturbed BH. Here we show that
this difficulty can be overcome by using multipolar inspiral-merger-ringdown
waveforms, calibrated to NR simulations, as already developed within the
effective-one-body formalism (EOBNR). We build a parameterized (nonspinning)
EOBNR waveform model in which the QNM complex frequencies are free parameters
(pEOBNR), and use Bayesian analysis to study its effectiveness in measuring
QNMs in GW150914, and in synthetic GW signals of BBHs injected in Gaussian
noise. We find that using the pEOBNR model gives, in general, stronger
constraints compared to the ones obtained when using a sum of damped sinusoids
and using Bayesian model selection, we also show that the pEOBNR model can
successfully be employed to find evidence for deviations from General
Relativity in the ringdown signal. Since the pEOBNR model properly includes
time and phase shifts among QNMs, it is also well suited to consistently
combine information from several observations --- e.g., we find on the order of
GW150914-like BBH events would be needed for Advanced LIGO and Virgo
at design sensitivity to measure the fundamental frequencies of both the
and modes, and the decay time of the mode with an
accuracy of at the 2\mbox{-}\sigma level, thus allowing to
test the BH's no-hair conjecture.Comment: 12 pages. v2: references added, discussion improved and 3 new
figures. Matches published versio
Density estimation with Gaussian processes for gravitational-wave posteriors
The properties of black-hole and neutron-star binaries are extracted from
gravitational-wave signals using Bayesian inference. This involves evaluating a
multi-dimensional posterior probability function with stochastic sampling. The
marginal probability density distributions from which the samples are drawn are
usually interpolated with kernel density estimators. Since most post-processing
analysis within the field is based on these parameter estimation products,
interpolation accuracy of the marginals is essential. In this work, we propose
a new method combining histograms and Gaussian Processes as an alternative
technique to fit arbitrary combinations of samples from the source parameters.
This method comes with several advantages such as flexible interpolation of
non-Gaussian correlations, Bayesian estimate of uncertainty, and efficient
re-sampling with Hamiltonian Monte Carlo
Basic Parameter Estimation of Binary Neutron Star Systems by the Advanced LIGO/Virgo Network
Within the next five years, it is expected that the Advanced LIGO/Virgo
network will have reached a sensitivity sufficient to enable the routine
detection of gravitational waves. Beyond the initial detection, the scientific
promise of these instruments relies on the effectiveness of our physical
parameter estimation capabilities. The majority of this effort has been towards
the detection and characterization of gravitational waves from compact binary
coalescence, e.g. the coalescence of binary neutron stars. While several
previous studies have investigated the accuracy of parameter estimation with
advanced detectors, the majority have relied on approximation techniques such
as the Fisher Matrix. Here we report the statistical uncertainties that will be
achievable for optimal detection candidates (SNR = 20) using the full parameter
estimation machinery developed by the LIGO/Virgo Collaboration via Markov-Chain
Monte Carlo methods. We find the recovery of the individual masses to be
fractionally within 9% (15%) at the 68% (95%) credible intervals for equal-mass
systems, and within 1.9% (3.7%) for unequal-mass systems. We also find that the
Advanced LIGO/Virgo network will constrain the locations of binary neutron star
mergers to a median uncertainty of 5.1 deg^2 (13.5 deg^2) on the sky. This
region is improved to 2.3 deg^2 (6 deg^2) with the addition of the proposed
LIGO India detector to the network. We also report the average uncertainties on
the luminosity distances and orbital inclinations of ideal detection candidates
that can be achieved by different network configurations.Comment: Second version: 15 pages, 9 figures, accepted in Ap
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