191 research outputs found
Measuring tidal effects with the Einstein Telescope: A design study
Over the last few years, there has been a large momentum to ensure that the
third-generation era of gravitational wave detectors will find its realisation
in the next decades, and numerous design studies have been ongoing for some
time. Some of the main factors determining the cost of the Einstein Telescope
lie in the length of the interferometer arms and its shape: L-shaped detectors
versus a single triangular configuration. Both designs are further expected to
include a xylophone configuration for improvement on both ends of the frequency
bandwidth of the detector. We consider binary neutron star sources in our
study, as examples of sources already observed with the current generation
detectors and ones which hold most promise given the broader frequency band and
higher sensitivity of the third-generation detectors. We estimate parameters of
the sources, with different kinds of configurations of the Einstein Telescope
detector, varying arm-lengths as well as shapes and alignments. Overall, we
find little improvement with respect to changing the shape, or alignment.
However, there are noticeable differences in the estimates of some parameters,
including tidal deformability, when varying the arm-length of the detectors. In
addition, we also study the effect of changing the laser power, and the lower
limit of the frequency band in which we perform the analysis.Comment: 11 pages, 7 figures, 4 table
Improving the NRTidal model for binary neutron star systems
Accurate and fast gravitational waveform (GW) models are essential to extract
information about the properties of compact binary systems that generate GWs.
Building on previous work, we present an extension of the NRTidal model for
binary neutron star (BNS) waveforms. The upgrades are: (i) a new closed-form
expression for the tidal contribution to the GW phase which includes further
analytical knowledge and is calibrated to more accurate numerical relativity
data than previously available; (ii) a tidal correction to the GW amplitude;
(iii) an extension of the spin-sector incorporating equation-of-state-dependent
finite size effects at quadrupolar and octupolar order; these appear in the
spin-spin tail terms and cubic-in-spin terms, both at 3.5PN. We add the new
description to the precessing binary black hole waveform model IMRPhenomPv2 to
obtain a frequency-domain precessing binary neutron star model. In addition, we
extend the SEOBNRv4_ROM and IMRPhenomD aligned-spin binary black hole waveform
models with the improved tidal phase corrections. Focusing on the new
IMRPhenomPv2_NRTidalv2 approximant, we test the model by comparing with
numerical relativity waveforms as well as hybrid waveforms combining tidal
effective-one-body and numerical relativity data. We also check consistency
against a tidal effective-one-body model across large regions of the BNS
parameter space.Comment: Accepted manuscrip
Biases in parameter estimation from overlapping gravitational-wave signals in the third generation detector era
In the past few years, the detection of gravitational waves from compact
binary coalescences with the Advanced LIGO and Advanced Virgo detectors has
become routine. Future observatories will detect even larger numbers of
gravitational-wave signals, which will also spend a longer time in the
detectors' sensitive band. This will eventually lead to overlapping signals,
especially in the case of Einstein Telescope (ET) and Cosmic Explorer (CE).
Using realistic distributions for the merger rate as a function of redshift as
well as for component masses in binary neutron star and binary black hole
coalescences, we map out how often signal overlaps of various types will occur
in an ET-CE network over the course of a year. We find that a binary neutron
star signal will typically have tens of overlapping binary black hole and
binary neutron star signals. Moreover, it will happen up to tens of thousands
of times per year that two signals will have their end times within seconds of
each other. In order to understand to what extent this would lead to
measurement biases with current parameter estimation methodology, we perform
injection studies with overlapping signals from binary black hole and/or binary
neutron star coalescences. Varying the signal-to-noise ratios, the durations of
overlap, and the kinds of overlapping signals, we find that in most scenarios
the intrinsic parameters can be recovered with negligible bias. However, biases
do occur for a short binary black hole or a quieter binary neutron star signal
overlapping with a long and louder binary neutron star event when the merger
times are sufficiently close. Hence our studies show where improvements are
required to ensure reliable estimation of source parameters for all detected
compact binary signals as we go from second-generation to third-generation
detectors.Comment: 15 pages, 11 figures, 12 table
Interpreting Binary Neutron Star Mergers: Describing the Binary Neutron Star Dynamics, Modelling Gravitational Waveforms, and Analyzing Detections
Gravitational waves emitted from the coalescence of neutron star binaries
open a new window to probe matter and fundamental physics in unexplored,
extreme regimes. To extract information about the supranuclear matter inside
neutron stars and the properties of the compact binary systems, robust
theoretical prescriptions are required. We give an overview about general
features of the dynamics and the gravitational wave signal during the binary
neutron star coalescence. We briefly describe existing analytical and numerical
approaches to investigate the highly dynamical, strong-field region during the
merger. We review existing waveform approximants and discuss properties and
possible advantages and shortcomings of individual waveform models, and their
application for real gravitational-wave data analysis.Comment: invited review for General Relativity and Gravitation; any comment or
suggestion is welcom
Parameter estimation methods for analyzing overlapping gravitational wave signals in the third-generation detector era
In the coming years, third-generation detectors such as the Einstein
Telescope and the Cosmic Explorer will enter the network of ground-based
gravitational-wave detectors. Their current design predicts a significantly
improved sensitivity band with a lower minimum frequency than existing
detectors. This, combined with the increased arm length, leads to two major
effects: the detection of more signals and the detection of longer signals.
Both will result in a large number of overlapping signals.
It has been shown that such overlapping signals can lead to biases in the
recovered parameters, which would adversely affect the science extracted from
the observed binary merger signals. In this work, we analyze overlapping binary
black hole coalescences with two methods to analyze multi-signal observations:
hierarchical subtraction and joint parameter estimation. We find that these
methods enable a reliable parameter extraction in most cases and that joint
parameter estimation is usually more precise but comes with higher
computational costs.Comment: 15 pages, 17 figure
A morphology-independent data analysis method for detecting and characterizing gravitational wave echoes
The ability to directly detect gravitational waves has enabled us to empirically probe the nature of ultracompact relativistic objects. Several alternatives to the black holes of classical general relativity have been proposed which do not have a horizon, in which case a newly formed object (e.g., as a result of binary merger) may emit echoes: bursts of gravitational radiation with varying amplitude and duration, but arriving at regular time intervals. Unlike in previous template-based approaches, we present a morphology-independent search method to find echoes in the data from gravitational wave detectors, based on a decomposition of the signal in terms of generalized wavelets consisting of multiple sine-Gaussians. The ability of the method to discriminate between echoes and instrumental noise is assessed by inserting into the noise two different signals: a train of sine-Gaussians, and an echoing signal from an extreme mass-ratio inspiral of a particle into a Schwarzschild vacuum spacetime, with reflective boundary conditions close to the horizon. We find that both types of signals are detectable for plausible signal-to-noise ratios in existing detectors and their near-future upgrades. Finally, we show how the algorithm can provide a characterization of the echoes in terms of the time between successive bursts, and damping and widening from one echo to the next
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