181 research outputs found
Probing dynamical spacetimes with gravitational waves
This decade will see the first direct detections of gravitational waves by
observatories such as Advanced LIGO and Virgo. Among the prime sources are
coalescences of binary neutron stars and black holes, which are ideal probes of
dynamical spacetime. This will herald a new era in the empirical study of
gravitation. For the first time, we will have access to the genuinely
strong-field dynamics, where low-energy imprints of quantum gravity may well
show up. In addition, we will be able to search for effects which might only
make their presence known at large distance scales, such as the ones that
gravitational waves must traverse in going from source to observer. Finally,
coalescing binaries can be used as cosmic distance markers, to study the
large-scale structure and evolution of the Universe.
With the advanced detector era fast approaching, concrete data analysis
algorithms are being developed to look for deviations from general relativity
in signals from coalescing binaries, taking into account the noisy detector
output as well as the expectation that most sources will be near the threshold
of detectability. Similarly, several practical methods have been proposed to
use them for cosmology. We explain the state of the art, including the
obstacles that still need to be overcome in order to make optimal use of the
signals that will be detected. Although the emphasis will be on
second-generation observatories, we will also discuss some of the science that
could be done with future third-generation ground-based facilities such as
Einstein Telescope, as well as with space-based detectors.Comment: 38 pages, 9 figures. Book chapter for the Springer Handbook of
Spacetime (Springer Verlag, to appear in 2013
A guide to LIGO-Virgo detector noise and extraction of transient gravitational-wave signals
The LIGO Scientific Collaboration and the Virgo Collaboration have cataloged eleven confidently detected gravitational-wave events during the first two observing runs of the advanced detector era. All eleven events were consistent with being from well-modeled mergers between compact stellar-mass objects: black holes or neutron stars. The data around the time of each of these events have been made publicly available through the gravitational-wave open science center. The entirety of the gravitational-wave strain data from the first and second observing runs have also now been made publicly available. There is considerable interest among the broad scientific community in understanding the data and methods used in the analyses. In this paper, we provide an overview of the detector noise properties and the data analysis techniques used to detect gravitational-wave signals and infer the source properties. We describe some of the checks that are performed to validate the analyses and results from the observations of gravitational-wave events. We also address concerns that have been raised about various properties of LIGO-Virgo detector noise and the correctness of our analyses as applied to the resulting data
Model comparison from LIGO-Virgo data on GW170817's binary components and consequences for the merger remnant
GW170817 is the very first observation of gravitational waves originating from the coalescence of two compact objects in the mass range of neutron stars, accompanied by electromagnetic counterparts, and offers an opportunity to directly probe the internal structure of neutron stars. We perform Bayesian model selection on a wide range of theoretical predictions for the neutron star equation of state. For the binary neutron star hypothesis, we find that we cannot rule out the majority of theoretical models considered. In addition, the gravitational-wave data alone does not rule out the possibility that one or both objects were low-mass black holes. We discuss the possible outcomes in the case of a binary neutron star merger, finding that all scenarios from prompt collapse to long-lived or even stable remnants are possible. For long-lived remnants, we place an upper limit of 1.9 kHz on the rotation rate. If a black hole was formed any time after merger and the coalescing stars were slowly rotating, then the maximum baryonic mass of non-rotating neutron stars is at most 3.05M⊙, and three equations of state considered here can be ruled out. We obtain a tighter limit of 2.67M⊙ for the case that the merger results in a hypermassive neutron star
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