21 research outputs found
Investigating the effect of in-plane spin directions for Precessing BBH systems
Morphology of coalescing BBH waveforms are affected by its spins. Waveform
models built for inference of source parameters have several in-built
approximations. In current precessing IMRPhenom and SEOBNR waveform models,
systems with the same spin magnitude but varying orientation of spins projected
on the orbital plane are effectively mapped to the same system (bar an overall
phase change) and the asymmetry due to precession between the and
modes is not modelled. In this study, we investigate the validity of these
approximations by generating numerical relativity (NR) simulations of
single-spin NR systems with varying in-plane spin directions (including several
superkick configurations) and provide an estimate of the SNR at which the
effect of varying in-plane spin directions would be measurable. This is done
computing the match between these waveforms and using these match values to
estimate the distinguishability SNR. We also use NR waveforms with different
spin magnitudes to compare the measurability of spin magnitude vs. in-plane
spin direction. We find that the in-plane spin direction could be measurable at
SNRs accessible by current generation detectors, with the distinguishability
SNR of varying in-plane spins comparable to or lower than varying the in-plane
spin magnitude. We then remove the mode-asymmetry content from the waveforms
and find that, i) removing mode-asymmetry increases the SNR at which in-plane
spin direction can be measured and ii) not modelling mode-asymmetry will lead
to measurement biases. The SNRs that we see at which the in-plane spins would
be measurable and at which mode-asymmetric content impacts the measurements are
the SNRs at which precession would be measurable, and we therefore conclude
that modelling in-plane spin direction and mode-asymmetry effects is necessary
for unbiassed measurements of precession.Comment: 13 pages, 8 figure
Modelling and studying gravitational waves from black-hole-binary mergers
The source parameters of the first direct detection (GW150914 [3]) of gravitational waves
(GW) from a binary black hole (BBH) system were determined by using approximate models
of the BBH coalescence, the errors on which could be driven by the noise (statistical
errors) or the approximate nature of the model (systematic errors). To determine the systematic
errors, a set of numerical relativity (NR) waveforms with similar parameters as of
GW150914 were injected over a range of inclination and polarisation values and recovered
with IMRPhenomPv2. The main result of this study was that the systematic errors induced
due to waveform model inaccuracies were much smaller than corresponding statistical errors,
and hence, the statistical errors dominate the systematic for the inferred parameters of
GW150914.
For current precessing waveform models, the six dimensional spin space is mapped to a
two dimensional space of effective spin parameters. We investigate the effects of changing
the in-plane spin direction on the GW signal and determine whether these effects are strong
enough to be measured by current ground based GW detectors. We also study the effect
of disregarding the mode-asymmetry content present in the signals and attempt to answer
whether mode-asymmetries need to be included in future waveform models.
GW signals, when decomposed in the spin weighted spherical harmonic basis, are made
of its different modes (hlms), with the quadrupole mode being dominant. The waveform
model IMRPhenomHM models a few of the sub-dominant modes with the quadrupole mode for
aligned-spin binaries. We wanted to investigate the effects of using a multimode (IMRPhenomHM)
and quadrupole only (IMRPhenomD) waveform model to recover source parameters from
multimode signals (IMRPhenomHM signals) and real physical signals (NR waveform signals)
across a range of physical parameters and inclination values
Parameter Estimation with a spinning multi-mode waveform model: IMRPhenomHM
Gravitational waves from compact binary coalescence sources can be decomposed
into spherical-harmonic multipoles, the dominant being the quadrupole () modes. The contribution of sub-dominant modes towards total signal
power increases with increasing binary mass ratio and source inclination to the
detector. It is well-known that in these cases neglecting higher modes could
lead to measurement biases, but these have not yet been quantified with a
higher-mode model that includes spin effects. In this study, we use the
multi-mode aligned-spin phenomenological waveform model IMRPhenomHM to
investigate the effects of including multi-mode content in estimating source
parameters and contrast the results with using a quadrupole-only model
(IMRPhenomD). We use as sources IMRPhenomHM and hybrid EOB-NR waveforms over a
range of mass-ratio and inclination combinations, and recover the parameters
with IMRPhenomHM and IMRPhenomD. These allow us to quantify the accuracy of
parameter measurements using a multi-mode model, the biases incurred when using
a quadrupole-only model to recover full (multi-mode) signals, and the
systematic errors in the IMRPhenomHM model. We see that the parameters
recovered by multi-mode templates are more precise for all non-zero
inclinations as compared to quadrupole templates. For multi-mode injections,
IMRPhenomD recovers biased parameters for non-zero inclinations with lower
likelihood while IMRPhenomHM recovered parameters are accurate for most cases,
and if a bias exists, it can be explained as a combined effect of observational
priors and (in the case of hybrid-NR signals) waveform inaccuracies. For cases
where IMRPhenomHM recovers biased parameters, the bias is always smaller than
the corresponding IMRPhenomD recovery, and we conclude that IMRPhenomHM will be
sufficiently accurate to allow unbiased measurements for most GW observations.Comment: 14 pages, 7 figure
First higher-multipole model of gravitational waves from spinning and coalescing black-hole binaries
Gravitational-wave observations of binary black holes currently rely on
theoretical models that predict the dominant multipoles (l,m) of the radiation
during inspiral, merger and ringdown. We introduce a simple method to include
the subdominant multipoles to binary black hole gravitational waveforms, given
a frequency-domain model for the dominant multipoles. The amplitude and phase
of the original model are appropriately stretched and rescaled using
post-Newtonian results (for the inspiral), perturbation theory (for the
ringdown), and a smooth transition between the two. No additional tuning to
numerical-relativity simulations is required. We apply a variant of this method
to the non-precessing PhenomD model. The result, PhenomHM, constitutes the
first higher-multipole model of spinning black-hole binaries, and currently
includes the (l,m) = (2,2), (3,3), (4,4), (2,1), (3,2), (4,3) radiative
moments. Comparisons with numerical-relativity waveforms demonstrate that
PhenomHM is more accurate than dominant-multipole-only models for all binary
configurations, and typically improves the measurement of binary properties.Comment: 4 pages, 4 figure
Unraveling information about supranuclear-dense matter from the complete binary neutron star coalescence process using future gravitational-wave detector networks
Gravitational waves provide us with an extraordinary tool to study the matter
inside neutron stars. In particular, the postmerger signal probes an extreme
temperature and density regime and will help reveal information about the
equation of state of supranuclear-dense matter. Although current detectors are
most sensitive to the signal emitted by binary neutron stars before the merger,
the upgrades of existing detectors and the construction of the next generation
of detectors will make postmerger detections feasible. For this purpose, we
present a new analytical, frequency-domain model for the
inspiral-merger-postmerger signal emitted by binary neutron stars systems. The
inspiral and merger part of the signals are modeled with IMRPhenomD_NRTidalv2,
and we describe the main emission peak of postmerger with a three-parameter
Lorentzian, using two different approaches: one in which the Lorentzian
parameters are kept free, and one in which we model them via quasi-universal
relations. We test the performance of our new complete waveform model in
parameter estimation analyses, studying simulated signals obtained from both
our developed model and by injecting numerical relativity waveforms. We
investigate the performance of different detector networks to determine the
improvement that future detectors will bring to our analysis. We consider
Advanced LIGO+ and Advanced Virgo+, KAGRA, and LIGO-India. We also study the
possible impact of a detector with high sensitivity in the kilohertz band like
NEMO, and finally we compare these results to the ones we obtain with
third-generation detectors, the Einstein Telescope and the Cosmic Explorer.Comment: Published versio
Testing general relativity using higher-order modes of gravitational waves from binary black holes
Recently, strong evidence was found for the presence of higher-order modes in the gravitational wave signals GW190412 and GW190814, which originated from compact binary coalescences with significantly asymmetric component masses. This has opened up the possibility of new tests of general relativity by looking at the way in which the higher-order modes are related to the basic signal. Here we further develop a test which assesses whether the amplitudes of subdominant harmonics are consistent with what is predicted by general relativity. To this end we incorporate a state-of-the-art waveform model with higher-order modes and precessing spins into a Bayesian parameter estimation and model selection framework. The analysis methodology is tested extensively through simulations. We investigate to what extent deviations in the relative amplitudes of the harmonics will be measurable depending on the properties of the source, and we map out correlations between our testing parameters and the inclination of the source with respect to the observer. Finally, we apply the test to GW190412 and GW190814, finding no evidence for violations of general relativity
Model of gravitational waves from precessing black-hole binaries through merger and ringdown
We present phenompnr, a frequency-domain phenomenological model of the gravitational-wave signal from binary-black-hole mergers that is tuned to numerical relativity (NR) simulations of precessing binaries. In many current waveform models, e.g., the âphenomâ and âeobnrâ families that have been used extensively to analyse LIGO-Virgo GW observations, analytic approximations are used to add precession effects to models of nonprecessing (aligned-spin) binaries, and it is only the aligned-spin models that are fully tuned to NR results. In phenompnr we incorporate precessing-binary numerical relativity results in two ways: (i) we produce the first numerical relativity-tuned model of the signal-based precession dynamics through merger and ringdown, and (ii) we extend a previous aligned-spin model, phenomd, to include the effects of misaligned spins on the signal in the coprecessing frame. The numerical relativity calibration has been performed on 40 simulations of binaries with mass ratios between
1
â¶
1
and
1
â¶
8
, where the larger black hole has a dimensionless spin magnitude of 0.4 or 0.8, and we choose five angles of spin misalignment with the orbital angular momentum. phenompnr has a typical mismatch accuracy within 0.1% up to mass ratio
1
â¶
4
and within 1% up to mass ratio
1
â¶
8