220 research outputs found
Bayesian Reconstruction of Gravitational-wave Signals from Binary Black Holes with Nonzero Eccentricities
We present a comprehensive study on how well gravitational-wave signals of
binary black holes with nonzero eccentricities can be recovered with state of
the art model-independent waveform reconstruction and parameter estimation
techniques. For this we use BayesWave, a Bayesian algorithm used by the
LIGO-Virgo Collaboration for unmodeled reconstructions of signal waveforms and
parameters. We used two different waveform models to produce simulated signals
of binary black holes with eccentric orbits and embed them in samples of
simulated noise of design-sensitivity Advanced LIGO detectors. We studied the
network overlaps and point estimates of central moments of signal waveforms
recovered by BayesWave as a function of , the eccentricity of the binary at
8 Hz orbital frequency. BayesWave recovers signals of near-circular
() and highly eccentric () binaries with network
overlaps similar to that of circular () ones, however it produces lower
network overlaps for binaries with . Estimation errors on
central frequencies and bandwidths (measured relative to bandwidths) are nearly
independent from , while estimation errors on central times and durations
(measured relative to durations) increase and decrease with above
, respectively. We also tested how BayesWave performs when
reconstructions are carried out using generalized wavelets with linear
frequency evolution (chirplets) instead of sine-Gaussian wavelets. We have
found that network overlaps improve by percent when chirplets are
used, and the improvement is the highest at low () eccentricities. There
is however no significant change in the estimation errors of central moments
when the chirplet base is used.Comment: 16 pages, 9 figures, accepted for publication in CQ
Constraints on coasting cosmological models from gravitational-wave standard sirens
We present the first test of coasting cosmological models with
gravitational-wave standard sirens observed in the first three observing runs
of the LIGO-Virgo-KAGRA detector network. We apply the statistical galaxy
catalog method adapted to coasting cosmologies and infer constraints on the
Hubble constant for the three fixed values of the curvature parameter
in units. The maximum posteriors
and highest density intervals we obtained from a combined analysis of
dark siren detections and a single bright siren detection are
, respectively. All our constraints on
are consistent within one sigma with the measured with the
differential age method, which provides a constraint on in coasting
cosmologies independently from . Our results constrain all cosmological
models with linear expansion in the luminosity distance and
redshift range of the LIGO-Virgo detections, i.e. and , which practically include all (both
strictly linear and quasi-linear) models in the coasting model family. As we
have found, the coasting models and the CDM model fit equally well to
the applied set of gravitational-wave detections.Comment: 7 pages, 3 figures, 1 tabl
Impact of modelling galaxy redshift uncertainties on the gravitational-wave dark standard siren measurement of the Hubble constant
Gravitational wave science is a new and rapidly expanding field of
observational astronomy. Multimessenger observations of the binary neutron star
merger GW170817 have provided some iconic results including the first
gravitational-wave standard-siren measurement of the Hubble constant, opening
up a new way to probe cosmology. The majority of the compact binary sources
observed in gravitational waves are however without bright electromagnetic
counterparts. In these cases, one can fall back on the ``dark standard siren''
approach to include information statistically from potential host galaxies. For
such a measurement, we need to be cautious about all possible sources of
systematic errors. In this paper, we begin to study the possible errors coming
from the galaxy catalogue sector, and in particular, look into the effect of
galaxy redshift uncertainties for the cases where these are photometry-based.
We recalculate the dark standard siren Hubble constant using the latest GWTC-3
events and associated galaxy catalogues, with different galaxy redshift
uncertainty models, namely, the standard Gaussian, a modified Lorentzian, and
no uncertainty at all. We find that not using redshift uncertainties at all can
lead to a potential bias comparable with other potential systematic effects
previously considered for the GWTC-3 measurement (however still small
compared to the overall statistical error in this measurement). The difference
between different uncertainty models leads to small differences in the results
for the current data; their impact is much smaller than the current statistical
errors and other potential sources of systematic errors which have been
considered in previous robustness studies.Comment: 9 pages, 8 figures, accepted to publication in MNRA
Attitude determination for nano-satellites – II. Dead reckoning with a multiplicative extended Kalman filter
This paper is the second part of a series of studies discussing a novel
attitude determination method for nano-satellites. Our approach is based on the
utilization of thermal imaging sensors to determine the direction of the Sun
and the nadir with respect to the satellite with sub-degree accuracy. The
proposed method is planned to be applied during the Cubesats Applied for
MEasuring and LOcalising Transients (CAMELOT) mission aimed at detecting and
localizing gamma-ray bursts with an efficiency and accuracy comparable to large
gamma-ray space observatories.
In this paper we introduce a simulation model aimed at testing the
applicability of our attitude determination approach. Its first part simulates
the orbit and rotation of a satellite with arbitrary initial conditions while
its second part applies our attitude determination algorithm which is based on
a multiplicative extended Kalman filter. The simulated satellite is assumed to
be equipped with a GPS system, MEMS gyroscopes and the infrasensors. These
instruments provide the required data input for the Kalman filter. We
demonstrate the applicability of our attitude determination algorithm by
simulating the motion of a nano-satellite on Low Earth Orbit. Our results show
that the attitude determination may have a 1 error of even
with a large gyroscope drift during the orbital periods when the infrasensors
provide both the direction of the Sun and the Earth (the nadir). This accuracy
is an improvement on the point source detection accuracy of the infrasensors.
However, the attitude determination error can get as high as 25
during periods when the Sun is occulted by the Earth. We show that following an
occultation period the attitude information is immediately recovered by the
Kalman filter once the Sun is observed again
Search for Transient Gravitational-wave Signals Associated with Magnetar Bursts during Advanced LIGO's Second Observing Run
We present the results of a search for short- and intermediate-duration gravitational-wave signals from four magnetar bursts in Advanced LIGO' s second observing run. We find no evidence of a signal and set upper bounds on the root sum squared of the total dimensionless strain (h(rss)) from incoming intermediate-duration gravitational waves ranging from 1.1 x 10(-22) at 150 Hz to 4.4 x 10(-22) at 1550 Hz at 50% detection efficiency. From the known distance to the magnetar SGR 1806-20 (8.7 kpc), we can place upper bounds on the isotropic gravitational-wave energy of 3.4 x 10(44) erg at 150 Hz assuming optimal orientation. This represents an improvement of about a factor of 10 in strain sensitivity from the previous search for such signals, conducted during initial LIGO' s sixth science run. The short-duration search yielded upper limits of 2.1 x 10(44) erg for short white noise bursts, and 2.3 x 10(47) erg for 100 ms long ringdowns at 1500 Hz, both at 50% detection efficiency
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