877 research outputs found
Astrophysical Sources of Stochastic Gravitational-Wave Background
We review the spectral properties of stochastic backgrounds of astrophysical
origin and discuss how they may differ from the primordial contribution by
their statistical properties. We show that stochastic searches with the next
generation of terrestrial interferometers could put interesting constrains on
the physical properties of astrophysical populations, such as the ellipticity
and magnetic field of magnetars, or the coalescence rate of compact binaries.Comment: 12 pages, 3 figures,accepted for publication in CQG, GWDAW12
conference proceedings version corrected in comparison published version
where we found an error in equation (4
A Semi-Parametric Approach to the Detection of Non-Gaussian Gravitational Wave Stochastic Backgrounds
Using a semi-parametric approach based on the fourth-order Edgeworth
expansion for the unknown signal distribution, we derive an explicit expression
for the likelihood detection statistic in the presence of non-normally
distributed gravitational wave stochastic backgrounds. Numerical likelihood
maximization exercises based on Monte-Carlo simulations for a set of large tail
symmetric non-Gaussian distributions suggest that the fourth cumulant of the
signal distribution can be estimated with reasonable precision when the ratio
between the signal and the noise variances is larger than 0.01. The estimation
of higher-order cumulants of the observed gravitational wave signal
distribution is expected to provide additional constraints on astrophysical and
cosmological models.Comment: 26 pages, 3 figures, to appear in Phys. Rev.
Second Einstein Telescope Mock Science Challenge : Detection of the GW Stochastic Background from Compact Binary Coalescences
We present the results of the search for an astrophysical gravitational-wave
stochastic background during the second Einstein Telescope mock data and
science challenge. Assuming that the loudest sources can be detected
individually and removed from the data, we show that the residual background
can be recovered with an accuracy of with the standard cross-correlation
statistic, after correction of a systematic bias due to the non-isotropy of the
sources.Comment: 15 pages, 4 figures, accepted for publication in Physical Review
Searching Gravitational Waves from Pulsars, Using Laser Beam Interferometers
We use recent population synthesis results to investigate the distribution of
pulsars in the frequency space, having a gravitational strain high enough to be
detected by the future generations of laser beam interferometers.
We find that until detectors become able to recover the entire population,
the frequency distribution of the 'detectable' population will be very
dependent on the detector noise curve. Assuming a mean equatorial deformation
, the optimal frequency is around 450 Hz for interferometers
of the first generation (LIGO or VIRGO) and shifts toward 85 Hz for advanced
detectors. An interesting result for future detection stategies is the
significant narrowing of the distribution when improving the sensitivity: with
an advanced detector, it is possible to have 90% of detection probability while
exploring less than 20% of the parameter space (7.5% in the case of ). In addition, we show that in most cases the spindown of
'detectable' pulsars represents a period shift of less than a tens of
nanoseconds after one year of observation, making them easier to follow in the
frequency space.Comment: 5 pages, 3 figures accepted for publication in Astronomy &
Astrophysic
Stochastic Gravitational Wave Background from Coalescing Binary Black Holes
We estimate the stochastic gravitational wave (GW) background signal from the
field population of coalescing binary stellar mass black holes (BHs) throughout
the Universe. This study is motivated by recent observations of BH-Wolf-Rayet
star systems and by new estimates in the metallicity abundances of star forming
galaxies that imply BH-BH systems are more common than previously assumed.
Using recent analytical results of the inspiral-merger-ringdown waveforms for
coalescing binary BH systems, we estimate the resulting stochastic GW
background signal. Assuming average quantities for the single source energy
emissions, we explore the parameter space of chirp mass and local rate density
required for detection by advanced and third generation interferometric GW
detectors. For an average chirp mass of 8.7, we find that detection
through 3 years of cross-correlation by two advanced detectors will require a
rate density, . Combining data from
multiple pairs of detectors can reduce this limit by up to 40%. Investigating
the full parameter space we find that detection could be achieved at rates for populations of coalescing binary BH
systems with average chirp masses of which are predicted by
recent studies of BH-Wolf-Rayet star systems. While this scenario is at the
high end of theoretical estimates, cross-correlation of data by two Einstein
Telescopes could detect this signal under the condition . Such a signal could potentially mask a primordial
GW background signal of dimensionless energy density, , around the (1--500) Hz frequency range.Comment: 22 pages, 5 figures, 2 tables, Accepted for publication by Ap
Measuring neutron-star ellipticity with measurements of the stochastic gravitational-wave background
Galactic neutron stars are a promising source of gravitational waves in the
analysis band of detectors such as LIGO and Virgo. Previous searches for
gravitational waves from neutron stars have focused on the detection of
individual neutron stars, which are either nearby or highly non-spherical. Here
we consider the stochastic gravitational-wave signal arising from the ensemble
of Galactic neutron stars. Using a population synthesis model, we estimate the
single-sigma sensitivity of current and planned gravitational-wave
observatories to average neutron star ellipticity as a function of
the number of in-band Galactic neutron stars . For the plausible
case of , and assuming one year of observation time
with colocated initial LIGO detectors, we find it to be
, which is comparable to current bounds on
some nearby neutron stars. (The current best upper limits are
) It is unclear if Advanced LIGO can
significantly improve on this sensitivity using spatially separated detectors.
For the proposed Einstein Telescope, we estimate that
. Finally, we show that stochastic
measurements can be combined with measurements of individual neutron stars in
order to estimate the number of in-band Galactic neutron stars. In this way,
measurements of stochastic gravitational waves provide a complementary tool for
studying Galactic neutron stars
Evidence for a dual population of neutron star mergers from short Gamma-Ray Burst observations
Short duration Gamma-Ray Bursts are thought to originate from the coalescence
of neutron stars in binary systems. They are detected as a brief ( 2s),
intense flash of gamma-ray radiation followed by a weaker, rapidly decreasing
afterglow. They are expected to be detected by Advanced LIGO and Virgo when
their sensitivity will be low enough. In a recent study we identified a
population of short Gamma-Ray Bursts that are intrinsically faint and nearby.
Here we provide evidence in favor of the existence of this new population that
can hardly be reproduced with a model of field neutron star binary
coalescences. We propose that these systems may be produced dynamically in
globular clusters, and may result from the merger of a black hole and a neutron
star. The advanced LIGO and Virgo observation of a high rate of NSBH mergers
compatible with the dynamical formation in globular clusters would be a
confirmation of this hypothesis and would enable for the derivation of the mass
function of black holes inside globular clusters, as well as the luminosity
function of faint short GRBs.Comment: 15 pages, 5 figures, 1 table, submitted to Ap
Parameter Estimation in Searches for the Stochastic Gravitational-Wave Background
The stochastic gravitational-wave background (SGWB) is expected to arise from
the superposition of many independent and unresolved gravitational-wave signals
of either cosmological or astrophysical origin. The spectral content of the
SGWB carries signatures of the physics that generated it. We present a Bayesian
framework for estimating the parameters associated with different SGWB models
using data from gravitational-wave detectors. We apply this technique to recent
results from LIGO to produce the first simultaneous 95% confidence level limits
on multiple parameters in generic power-law SGWB models and in SGWB models of
compact binary coalescences. We also estimate the sensitivity of the upcoming
second-generation detectors such as Advanced LIGO/Virgo to these models and
demonstrate how SGWB measurements can be combined and compared with
observations of individual compact binary coalescences in order to build
confidence in the origin of an observed SGWB signal. In doing so, we
demonstrate a novel means of differentiating between different sources of the
SGWB.Comment: 6 pages, 5 figure
- …