766 research outputs found
Constraints on Kerr-Newman black holes from merger-ringdown gravitational-wave observations
We construct a template to model the post-merger phase of a binary black hole
coalescence in the presence of a remnant charge. We include the
quasi-normal modes typically dominant during a binary black hole coalescence,
and also present analytical fits for the
quasinormal mode frequencies of a Kerr-Newman black hole in terms of its spin
and charge, here also including the mode. Aside from astrophysical
electric charge, our template can accommodate extensions of the Standard Model,
such as a dark photon. Applying the model to LIGO-Virgo detections, we find
that we are unable to distinguish between the charged and uncharged hypotheses
from a purely post-merger analysis of the current events. However, restricting
the mass and spin to values compatible with the analysis of the full signal, we
obtain a 90th percentile bound on the black hole
charge-to-mass ratio, for the most favorable case of GW150914. Under similar
assumptions, by simulating a typical loud signal observed by the LIGO-Virgo
network at its design sensitivity, we assess that this model can provide a
robust measurement of the charge-to-mass ratio only for values ; here we also assume that the mode amplitudes are similar to the uncharged
case in creating our simulated signal. Lower values, down to , could instead be detected when evaluating the consistency of the
pre-merger and post-merger emission.Comment: 21 pages, 11 figures, 4 tables. Matches published versio
TIGER: A data analysis pipeline for testing the strong-field dynamics of general relativity with gravitational wave signals from coalescing compact binaries
Population inference of spin-induced quadrupole moments as a probe for non-black hole compact binaries
Gravitational-wave (GW) measurements of physical effects such as spin-induced
quadrupole moments can distinguish binaries consisting of black holes from
non-black hole binaries. While these effects may be poorly constrained for
single-event inferences with the second-generation detectors, combining
information from multiple detections can help uncover features of non-black
hole binaries. The spin-induced quadrupole moment has specific predictions for
different types of compact objects, and a generalized formalism must consider a
population where different types of compact objects co-exist. In this study, we
introduce a hierarchical mixture-likelihood formalism to estimate the {\it
fraction of non-binary black holes in the population}. We demonstrate the
applicability of this method using simulated GW signals injected into Gaussian
noise following the design sensitivities of the Advanced LIGO Advanced Virgo
detectors. We compare the performance of this method with a
traditionally-followed hierarchical inference approach. Both the methods are
equally effective to hint at inhomogeneous populations, however, we find the
mixture-likelihood approach to be more natural for mixture populations
comprising compact objects of diverse classes. We also discuss the possible
systematics in the mixture-likelihood approach, caused by several reasons,
including the limited sensitivity of the second-generation detectors, specific
features of the astrophysical population distributions, and the limitations
posed by the waveform models employed. Finally, we apply this method to the
LIGO-Virgo detections published in the second GW transient catalog (GWTC-2) and
find them consistent with a binary black hole population within the statistical
precision.Comment: 13 pages, 6 figures, 1 tabl
Constraining the neutron star equation of state with gravitational wave signals from coalescing binary neutron stars
Recently exploratory studies were performed on the possibility of constraining the neutron star equation of state (EOS) using signals from coalescing binary neutron stars, or neutron star–black hole systems, as they will be seen in upcoming advanced gravitational wave detectors such as Advanced LIGO and Advanced Virgo. In particular, it was estimated to what extent the combined information from multiple detections would enable one to distinguish between different equations of state through hypothesis ranking or parameter estimation. Under the assumption of zero neutron star spins both in signals and in template waveforms and considering tidal effects to 1 post-Newtonian (1PN) order, it was found that O(20) sources would suffice to distinguish between a stiff, moderate, and soft equation of state. Here we revisit these results, this time including neutron star tidal effects to the highest order currently known, termination of gravitational waveforms at the contact frequency, neutron star spins, and the resulting quadrupole-monopole interaction. We also take the masses of neutron stars in simulated sources to be distributed according to a relatively strongly peaked Gaussian, as hinted at by observations, but without assuming that the data analyst will necessarily have accurate knowledge of this distribution for use as a mass prior. We find that especially the effect of the latter is dramatic, necessitating many more detections to distinguish between different EOSs and causing systematic biases in parameter estimation, on top of biases due to imperfect understanding of the signal model pointed out in earlier work. This would get mitigated if reliable prior information about the mass distribution could be folded into the analyses
Towards a generic test of the strong field dynamics of general relativity using compact binary coalescence: Further investigations
In this paper we elaborate on earlier work by the same authors in which a
novel Bayesian inference framework for testing the strong-field dynamics of
General Relativity using coalescing compact binaries was proposed. Unlike
methods that were used previously, our technique addresses the question whether
one or more 'testing coefficients' (e.g. in the phase) parameterizing
deviations from GR are non-zero, rather than all of them differing from zero at
the same time. The framework is well-adapted to a scenario where most sources
have low signal-to-noise ratio, and information from multiple sources as seen
in multiple detectors can readily be combined. In our previous work, we
conjectured that this framework can detect generic deviations from GR that can
in principle not be accomodated by our model waveforms, on condition that the
change in phase near frequencies where the detectors are the most sensitive is
comparable to that induced by simple shifts in the lower-order phase
coefficients of more than a few percent ( radians at 150 Hz). To
further support this claim, we perform additional numerical experiments in
Gaussian and stationary noise according to the expected Advanced LIGO/Virgo
noise curves, and coherently injecting signals into the network whose phasing
differs structurally from the predictions of GR, but with the magnitude of the
deviation still being small. We find that even then, a violation of GR can be
established with good confidence.Comment: 15 pages, 7 figures, Amaldi 9 proceeding
Triple Michelson Interferometer for a Third-Generation Gravitational Wave Detector
The upcoming European design study `Einstein gravitational-wave Telescope'
represents the first step towards a substantial, international effort for the
design of a third-generation interferometric gravitational wave detector. It is
generally believed that third-generation instruments might not be installed
into existing infrastructures but will provoke a new search for optimal
detector sites. Consequently, the detector design could be subject to fewer
constraints than the on-going design of the second generation instruments. In
particular, it will be prudent to investigate alternatives to the traditional
L-shaped Michelson interferometer. In this article, we review an old proposal
to use three Michelson interferometers in a triangular configuration. We use
this example of a triple Michelson interferometer to clarify the terminology
and will put this idea into the context of more recent research on
interferometer technologies. Furthermore the benefits of a triangular detector
will be used to motivate this design as a good starting point for a more
detailed research effort towards a third-generation gravitational wave
detector.Comment: Minor corrections to the main text and two additional appendices. 14
pages, 6 figure
Effect of calibration errors on Bayesian parameter estimation for gravitational wave signals from inspiral binary systems in the advanced detectors era: Further investigations
By 2015, the advanced versions of the gravitational wave detectors Virgo and LIGO will be online. They will collect data in coincidence with enough sensitivity to potentially deliver multiple detections of gravitational waves from inspirals of compact-object binaries. In a previous work, we have studied the effects introduced in the estimation of the physical parameters of the source by uncertainties in the calibration of the interferometers. Our bias estimator for parameter errors introduced by calibration uncertainties consisted of two terms: A genuine bias due to the calibration errors, and a contribution coming from the limited number of samples used to explore the parameter space. In this article, we have focused on this second term, and we have shown how it is smaller than the former (about 10 times smaller), and how it decreases as the signal-to-noise rati
Inference of the cosmological parameters from gravitational waves: application to second generation interferometers
The advanced world-wide network of gravitational waves (GW) observatories is
scheduled to begin operations within the current decade. Thanks to their
improved sensitivity, they promise to yield a number of detections and thus to
open a new observational windows for astronomy and astrophysics. Among the
scientific goals that should be achieved, there is the independent measurement
of the value of the cosmological parameters, hence an independent test of the
current cosmological paradigm. Due to the importance of such task, a number of
studies have evaluated the capabilities of GW telescopes in this respect.
However, since GW do not yield information about the source redshift, different
groups have made different assumptions regarding the means through which the GW
redshift can be obtained. These different assumptions imply also different
methodologies to solve this inference problem. This work presents a formalism
based on Bayesian inference developed to facilitate the inclusion of all
assumptions and prior information about a GW source within a single data
analysis framework. This approach guarantees the minimisation of information
loss and the possibility of including naturally event-specific knowledge (such
as the sky position for a Gamma Ray Burst - GW coincident observation) in the
analysis. The workings of the method are applied to a specific example, loosely
designed along the lines of the method proposed by Schutz in 1986, in which one
uses information from wide-field galaxy surveys as prior information for the
location of a GW source. I show that combining the results from few tens of
observations from a network of advanced interferometers will constrain the
Hubble constant to an accuracy of % at 95% confidence.Comment: 13 pages, 25 figures. Accepted for publication in Phys. Rev.
Towards a generic test of the strong field dynamics of general relativity using compact binary coalescence
Coalescences of binary neutron stars and/or black holes are amongst the most
likely gravitational-wave signals to be observed in ground based
interferometric detectors. Apart from the astrophysical importance of their
detection, they will also provide us with our very first empirical access to
the genuinely strong-field dynamics of General Relativity (GR). We present a
new framework based on Bayesian model selection aimed at detecting deviations
from GR, subject to the constraints of the Advanced Virgo and LIGO detectors.
The method tests the consistency of coefficients appearing in the waveform with
the predictions made by GR, without relying on any specific alternative theory
of gravity. The framework is suitable for low signal-to-noise ratio events
through the construction of multiple subtests, most of which involve only a
limited number of coefficients. It also naturally allows for the combination of
information from multiple sources to increase one's confidence in GR or a
violation thereof. We expect it to be capable of finding a wide range of
possible deviations from GR, including ones which in principle cannot be
accommodated by the model waveforms, on condition that the induced change in
phase at frequencies where the detectors are the most sensitive is comparable
to the effect of a few percent change in one or more of the low-order
post-Newtonian phase coefficients. In principle the framework can be used with
any GR waveform approximant, with arbitrary parameterized deformations, to
serve as model waveforms. In order to illustrate the workings of the method, we
perform a range of numerical experiments in which simulated gravitational waves
modeled in the restricted post-Newtonian, stationary phase approximation are
added to Gaussian and stationary noise that follows the expected Advanced
LIGO/Virgo noise curves.Comment: 26 pages, 23 figures, Accepted by PR
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