580 research outputs found
Waveform accuracy and systematic uncertainties in current gravitational wave observations
The post-Newtonian formalism plays an integral role in the models used to
extract information from gravitational wave data, but models that incorporate
this formalism are inherently approximations. Disagreement between an
approximate model and nature will produce mismodeling biases in the parameters
inferred from data, introducing systematic error. We here carry out a
proof-of-principle study of such systematic error by considering signals
produced by quasi-circular, inspiraling black hole binaries through an
injection and recovery campaign. In particular, we study how unknown, but
calibrated, higher-order post-Newtonian corrections to the gravitational wave
phase impact systematic error in recovered parameters. As a first study, we
produce injected data of non-spinning binaries as detected by a current,
second-generation network of ground-based observatories and recover them with
models of varying PN order in the phase. We find that the truncation of higher
order (>3.5) post-Newtonian corrections to the phase can produce significant
systematic error even at signal-to-noise ratios of current detector networks.
We propose a method to mitigate systematic error by marginalizing over our
ignorance in the waveform through the inclusion of higher-order post-Newtonian
coefficients as new model parameters. We show that this method can reduce
systematic error greatly at the cost of increasing statistical error.Comment: 14 pages, 7 figure
Targeted large mass ratio numerical relativity surrogate waveform model for GW190814
Gravitational wave observations of large mass ratio compact binary mergers like GW190814 highlight the need for reliable, high-accuracy waveform templates for such systems. We present NRHybSur2dq15, a new surrogate model trained on hybridized numerical relativity (NR) waveforms with mass ratios , and aligned spins and . We target the parameter space of GW190814-like events as large mass ratio NR simulations are very expensive. The model includes the (2,2), (2,1), (3,3), (4,4), and (5,5) spin-weighted spherical harmonic modes, and spans the entire LIGO bandwidth (with Hz) for total masses . NRHybSur2dq15 accurately reproduces the hybrid waveforms, with mismatches below for total masses . This is at least an order of magnitude improvement over existing semi-analytical models for GW190814-like systems. Finally, we reanalyze GW190814 with the new model and obtain source parameter constraints consistent with previous work
Early Advanced LIGO binary neutron-star sky localization and parameter estimation
2015 will see the first observations of Advanced LIGO and the start of the
gravitational-wave (GW) advanced-detector era. One of the most promising
sources for ground-based GW detectors are binary neutron-star (BNS)
coalescences. In order to use any detections for astrophysics, we must
understand the capabilities of our parameter-estimation analysis. By simulating
the GWs from an astrophysically motivated population of BNSs, we examine the
accuracy of parameter inferences in the early advanced-detector era. We find
that sky location, which is important for electromagnetic follow-up, can be
determined rapidly (~5 s), but that sky areas may be hundreds of square
degrees. The degeneracy between component mass and spin means there is
significant uncertainty for measurements of the individual masses and spins;
however, the chirp mass is well measured (typically better than 0.1%).Comment: 4 pages, 2 figures. Published in the proceedings of Amaldi 1
Mitigation of the instrumental noise transient in gravitational-wave data surrounding GW170817
In the coming years gravitational-wave detectors will undergo a series of
improvements, with an increase in their detection rate by about an order of
magnitude. Routine detections of gravitational-wave signals promote novel
astrophysical and fundamental theory studies, while simultaneously leading to
an increase in the number of detections temporally overlapping with
instrumentally- or environmentally-induced transients in the detectors
(glitches), often of unknown origin. Indeed, this was the case for the very
first detection by the LIGO and Virgo detectors of a gravitational-wave signal
consistent with a binary neutron star coalescence, GW170817. A loud glitch in
the LIGO-Livingston detector, about one second before the merger, hampered
coincident detection (which was initially achieved solely with LIGO-Hanford
data). Moreover, accurate source characterization depends on specific
assumptions about the behavior of the detector noise that are rendered invalid
by the presence of glitches. In this paper, we present the various techniques
employed for the initial mitigation of the glitch to perform source
characterization of GW170817 and study advantages and disadvantages of each
mitigation method. We show that, despite the presence of instrumental noise
transients louder than the one affecting GW170817, we are still able to produce
unbiased measurements of the intrinsic parameters from simulated injections
with properties similar to GW170817.Comment: 11 pages, 3 figures, accepted in PR
Full band all-sky search for periodic gravitational waves in the O1 LIGO data
We report on a new all-sky search for periodic gravitational waves in the frequency band 475-2000 Hz and with a frequency time derivative in the range of [-1.0,+0.1]×10-8 Hz/s. Potential signals could be produced by a nearby spinning and slightly nonaxisymmetric isolated neutron star in our Galaxy. This search uses the data from Advanced LIGO\u27s first observational run O1. No gravitational-wave signals were observed, and upper limits were placed on their strengths. For completeness, results from the separately published low-frequency search 20-475 Hz are included as well. Our lowest upper limit on worst-case (linearly polarized) strain amplitude h0 is ∼4×10-25 near 170 Hz, while at the high end of our frequency range, we achieve a worst-case upper limit of 1.3×10-24. For a circularly polarized source (most favorable orientation), the smallest upper limit obtained is ∼1.5×10-25
First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data
Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of
continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a
fully coherent search, based on matched filtering, which uses the position and rotational parameters
obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signalto-
noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch
between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have
been developed, allowing a fully coherent search for gravitational waves from known pulsars over a
fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of
11 pulsars using data from Advanced LIGO’s first observing run. Although we have found several initial
outliers, further studies show no significant evidence for the presence of a gravitational wave signal.
Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of
the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for
the first time. For an additional 3 targets, the median upper limit across the search bands is below the
spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried
out so far
Robust parameter estimation for compact binaries with ground-based gravitational-wave observations using the LALInference software library
The Advanced LIGO and Advanced Virgo gravitational wave (GW) detectors will
begin operation in the coming years, with compact binary coalescence events a
likely source for the first detections. The gravitational waveforms emitted
directly encode information about the sources, including the masses and spins
of the compact objects. Recovering the physical parameters of the sources from
the GW observations is a key analysis task. This work describes the
LALInference software library for Bayesian parameter estimation of compact
binary signals, which builds on several previous methods to provide a
well-tested toolkit which has already been used for several studies. We show
that our implementation is able to correctly recover the parameters of compact
binary signals from simulated data from the advanced GW detectors. We
demonstrate this with a detailed comparison on three compact binary systems: a
binary neutron star, a neutron star black hole binary and a binary black hole,
where we show a cross-comparison of results obtained using three independent
sampling algorithms. These systems were analysed with non-spinning, aligned
spin and generic spin configurations respectively, showing that consistent
results can be obtained even with the full 15-dimensional parameter space of
the generic spin configurations. We also demonstrate statistically that the
Bayesian credible intervals we recover correspond to frequentist confidence
intervals under correct prior assumptions by analysing a set of 100 signals
drawn from the prior. We discuss the computational cost of these algorithms,
and describe the general and problem-specific sampling techniques we have used
to improve the efficiency of sampling the compact binary coalescence parameter
space
Characterizing Gravitational Wave Detector Networks: From A to Cosmic Explorer
Gravitational-wave observations by the Laser Interferometer
Gravitational-Wave Observatory (LIGO) and Virgo have provided us a new tool to
explore the universe on all scales from nuclear physics to the cosmos and have
the massive potential to further impact fundamental physics, astrophysics, and
cosmology for decades to come. In this paper we have studied the science
capabilities of a network of LIGO detectors when they reach their best possible
sensitivity, called A#, and a new generation of observatories that are factor
of 10 to 100 times more sensitive (depending on the frequency), in particular a
pair of L-shaped Cosmic Explorer observatories (one 40 km and one 20 km arm
length) in the US and the triangular Einstein Telescope with 10 km arms in
Europe. We use a set of science metrics derived from the top priorities of
several funding agencies to characterize the science capabilities of different
networks. The presence of one or two A# observatories in a network containing
two or one next generation observatories, respectively, will provide good
localization capabilities for facilitating multimessenger astronomy and
precision measurement of the Hubble parameter. A network of two Cosmic Explorer
observatories and the Einstein Telescope is critical for accomplishing all the
identified science metrics including the nuclear equation of state,
cosmological parameters, growth of black holes through cosmic history, and make
new discoveries such as the presence of dark matter within or around neutron
stars and black holes, continuous gravitational waves from rotating neutron
stars, transient signals from supernovae, and the production of stellar-mass
black holes in the early universe. For most metrics the triple network of next
generation terrestrial observatories are a factor 100 better than what can be
accomplished by a network of three A# observatories.Comment: 45 pages, 20 figure
Bayesian inference for compact binary coalescences with BILBY:Validation and application to the first LIGO-Virgo gravitational-wave transient catalogue
Gravitational waves provide a unique tool for observational astronomy. While the first LIGO–Virgo catalogue of gravitational-wave transients (GWTC-1) contains eleven signals from black hole and neutron star binaries, the number of observations is increasing rapidly as detector sensitivity improves. To extract information from the observed signals, it is imperative to have fast, flexible, and scalable inference techniques. In a previous paper, we introduced BILBY: a modular and user-friendly Bayesian inference library adapted to address the needs of gravitational-wave inference. In this work, we demonstrate that BILBY produces reliable results for simulated gravitational-wave signals from compact binary mergers, and verify that it accurately reproduces results reported for the eleven GWTC-1 signals. Additionally, we provide configuration and output files for all analyses to allow for easy reproduction, modification, and future use. This work establishes that BILBY is primed and ready to analyse the rapidly growing population of compact binary coalescence gravitational-wave signals
First measurement of the Hubble Constant from a Dark Standard Siren using the Dark Energy Survey Galaxies and the LIGO/Virgo Binary–Black-hole Merger GW170814
International audienceWe present a multi-messenger measurement of the Hubble constant H 0 using the binary–black-hole merger GW170814 as a standard siren, combined with a photometric redshift catalog from the Dark Energy Survey (DES). The luminosity distance is obtained from the gravitational wave signal detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo Collaboration (LVC) on 2017 August 14, and the redshift information is provided by the DES Year 3 data. Black hole mergers such as GW170814 are expected to lack bright electromagnetic emission to uniquely identify their host galaxies and build an object-by-object Hubble diagram. However, they are suitable for a statistical measurement, provided that a galaxy catalog of adequate depth and redshift completion is available. Here we present the first Hubble parameter measurement using a black hole merger. Our analysis results in , which is consistent with both SN Ia and cosmic microwave background measurements of the Hubble constant. The quoted 68% credible region comprises 60% of the uniform prior range [20, 140] km s−1 Mpc−1, and it depends on the assumed prior range. If we take a broader prior of [10, 220] km s−1 Mpc−1, we find (57% of the prior range). Although a weak constraint on the Hubble constant from a single event is expected using the dark siren method, a multifold increase in the LVC event rate is anticipated in the coming years and combinations of many sirens will lead to improved constraints on H 0
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