939 research outputs found
Comment on "Analysis of Ringdown Overtones in GW150914''
Cotesta et al. (2022) reanalyze the GW150914 ringdown, arguing against the
presence of an overtone and suggesting claims of its detection in Isi et al.
(2019) were driven by noise. Here we point out a number of technical errors in
that analysis, including a software bug, and show that features highlighted as
problematic are in fact expected and encountered in simulated data. After
fixes, the code in used in Cotesta et al. (2022) produces results consistent
with the presence of the overtone. All code and data are available at
https://github.com/maxisi/gw150914_rd_commentComment: 2 pages, 2 figures; a reproducible article prepared with ShowYourWork
hosted at https://github.com/maxisi/gw150914_rd_commen
Testing the no-hair theorem with GW150914
We analyze gravitational-wave data from the first LIGO detection of a binary
black-hole merger (GW150914) in search of the ringdown of the remnant black
hole. Using observations beginning at the peak of the signal, we find evidence
of the fundamental quasinormal mode and at least one overtone, both associated
with the dominant angular mode (), with confidence. A
ringdown model including overtones allows us to measure the final mass and spin
magnitude of the remnant exclusively from postinspiral data, obtaining an
estimate in agreement with the values inferred from the full signal. The mass
and spin values we measure from the ringdown agree with those obtained using
solely the fundamental mode at a later time, but have smaller uncertainties.
Agreement between the postinspiral measurements of mass and spin and those
using the full waveform supports the hypothesis that the GW150914 merger
produced a Kerr black hole, as predicted by general relativity, and provides a
test of the no-hair theorem at the level. An independent
measurement of the frequency of the first overtone yields agreement with the
no-hair hypothesis at the level. As the detector sensitivity
improves and the detected population of black hole mergers grows, we can expect
that using overtones will provide even stronger tests.Comment: v2: journal versio
Comment on "Analysis of Ringdown Overtones in GW150914''
Cotesta et al. (2022) reanalyze the GW150914 ringdown, arguing against the
presence of an overtone and suggesting claims of its detection in Isi et al.
(2019) were driven by noise. Here we point out a number of technical errors in
that analysis, including a software bug, and show that features highlighted as
problematic are in fact expected and encountered in simulated data. After
fixes, the code in used in Cotesta et al. (2022) produces results consistent
with the presence of the overtone. All code and data are available at
https://github.com/maxisi/gw150914_rd_commentComment: 2 pages, 2 figures; a reproducible article prepared with ShowYourWork
hosted at https://github.com/maxisi/gw150914_rd_commen
Machine-learning nonstationary noise out of gravitational-wave detectors
Signal extraction out of background noise is a common challenge in high-precision physics experiments, where the measurement output is often a continuous data stream. To improve the signal-to-noise ratio of the detection, witness sensors are often used to independently measure background noises and subtract them from the main signal. If the noise coupling is linear and stationary, optimal techniques already exist and are routinely implemented in many experiments. However, when the noise coupling is nonstationary, linear techniques often fail or are suboptimal. Inspired by the properties of the background noise in gravitational wave detectors, this work develops a novel algorithm to efficiently characterize and remove nonstationary noise couplings, provided there exist witnesses of the noise source and of the modulation. In this work, the algorithm is described in its most general formulation, and its efficiency is demonstrated with examples from the data of the Advanced LIGO gravitational-wave observatory, where we could obtain an improvement of the detector gravitational-wave reach without introducing any bias on the source parameter estimation
The directional isotropy of LIGO-Virgo binaries
We demonstrate how to constrain the degree of absolute alignment of the total
angular momenta of LIGO-Virgo binary black holes, looking for a special
direction in space that would break isotropy. We also allow for inhomogeneities
in the distribution of black holes over the sky. Making use of dipolar models
for the spatial distribution and orientation of the sources, we analyze 57
signals with false-alarm rates < 1/yr from the third LIGO-Virgo observing run.
Accounting for selection biases, we find the population of LIGO-Virgo black
holes to be fully consistent with both homogeneity and isotropy. We
additionally find the data to constrain some directions of alignment more than
others, and produce posteriors for the directions of total angular momentum of
all binaries in our set. All code and data are made publicly available in
https://github.com/maxisi/gwisotropy/
Hierarchical Test of General Relativity with Gravitational Waves
We propose a hierarchical approach to testing general relativity with multiple gravitational wave detections. Unlike existing strategies, our method does not assume that parameters quantifying deviations from general relativity are either common or completely unrelated across all sources. We instead assume that these parameters follow some underlying distribution, which we parametrize and constrain. This can be then compared to the distribution expected from general relativity, i.e., no deviation in any of the events. We demonstrate that our method is robust to measurement uncertainties and can be applied to theories of gravity where the parameters beyond general relativity are related to each other, as generally expected. Our method contains the two extremes of common and unrelated parameters as limiting cases. We apply the hierarchical model to the population of 10 binary black hole systems so far detected by LIGO and Virgo. We do this for a parametrized test of gravitational wave generation, by modeling the population distribution of beyond-general-relativity parameters with a Gaussian distribution. We compute the mean and the variance of the population and show that both are consistent with general relativity for all parameters we consider. In the best case, we find that the population properties of the existing binary signals are consistent with general relativity at the ∼1% level. This hierarchical approach subsumes and extends existing methodologies and is more robust at revealing potential subtle deviations from general relativity with increasing number of detections
Fortifying gravitational-wave tests of general relativity against astrophysical assumptions
Most tests of general relativity with gravitational-wave observations rely on
inferring the degree to which a signal deviates from general relativity in
conjunction with the astrophysical parameters of its source, such as the
component masses and spins of a compact binary. Due to features of the signal,
measurements of these deviations are often highly correlated with the
properties of astrophysical sources. As a consequence, prior assumptions about
astrophysical parameters will generally affect the inferred magnitude of the
deviations. Incorporating information about the underlying astrophysical
population is necessary to avoid biases in the inference of deviations from
general relativity. Current tests assume that the astrophysical population
follows an unrealistic fiducial prior chosen to ease sampling of the posterior
-- for example, a prior flat in component masses -- which is is inconsistent
with both astrophysical expectations and the distribution inferred from
observations. We propose a framework for fortifying tests of general relativity
by simultaneously inferring the astrophysical population using a catalog of
detections. Although this method applies broadly, we demonstrate it concretely
on massive graviton constraints and parameterized tests of deviations to the
post-Newtonian phase coefficients. Using observations from LIGO-Virgo-KAGRA's
third observing run, we show that concurrent inference of the astrophysical
distribution strengthens constraints and improves overall consistency with
general relativity. We provide updated constraints on deviations from the
theory, finding that, upon modeling the astrophysical population, the
90\%-credible upper limit on the mass of the graviton improves by to
and the inferred
population-level post-Newtonian deviations move closer to
zero.Comment: 20 pages, 11 figure
Hints of spin-orbit resonances in the binary black hole population
Binary black hole spin measurements from gravitational wave observations can reveal the binary's evolutionary history. In particular, the spin orientations of the component black holes within the orbital plane, and , can be used to identify binaries caught in the so-called spin-orbit resonances. In a companion paper, we demonstrate that and are best measured near the merger of the two black holes. In this work, we use these spin measurements to provide the first constraints on the full six-dimensional spin distribution of merging binary black holes. In particular, we find that there is a preference for in the population, which can be a signature of spin-orbit resonances. We also find a preference for with respect to the line of separation near merger, which has not been predicted for any astrophysical formation channel. However, the strength of these preferences depends on our prior choices, and we are unable to constrain the widths of the and distributions. Therefore, more observations are necessary to confirm the features we find. Finally, we derive constraints on the distribution of recoil kicks in the population, and use this to estimate the fraction of merger remnants retained by globular and nuclear star clusters. We make our spin and kick population constraints publicly available
Measuring binary black hole orbital-plane spin orientations
Binary black hole spins are among the key observables for gravitational wave astronomy. Among the spin parameters, their orientations within the orbital plane, , and , are critical for understanding the prevalence of the spin-orbit resonances and merger recoils in binary black holes. Unfortunately, these angles are particularly hard to measure using current detectors, LIGO and Virgo. Because the spin directions are not constant for precessing binaries, the traditional approach is to measure the spin components at some reference stage in the waveform evolution, typically the point at which the frequency of the detected signal reaches 20 Hz. However, we find that this is a poor choice for the orbital-plane spin angle measurements. Instead, we propose measuring the spins at a fixed dimensionless time or frequency near the merger. This leads to significantly improved measurements for and for several gravitational wave events. Furthermore, using numerical relativity injections, we demonstrate that will also be better measured near the merger for louder signals expected in the future. Finally, we show that numerical relativity surrogate models are key for reliably measuring the orbital-plane spin orientations, even at moderate signal-to-noise ratios like
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