38,596 research outputs found
Detection of a close supernova gravitational wave burst in a network of interferometers, neutrino and optical detectors
Trying to detect the gravitational wave (GW) signal emitted by a type II
supernova is a main challenge for the GW community. Indeed, the corresponding
waveform is not accurately modeled as the supernova physics is very complex; in
addition, all the existing numerical simulations agree on the weakness of the
GW emission, thus restraining the number of sources potentially detectable.
Consequently, triggering the GW signal with a confidence level high enough to
conclude directly to a detection is very difficult, even with the use of a
network of interferometric detectors. On the other hand, one can hope to take
benefit from the neutrino and optical emissions associated to the supernova
explosion, in order to discover and study GW radiation in an event already
detected independently. This article aims at presenting some realistic
scenarios for the search of the supernova GW bursts, based on the present
knowledge of the emitted signals and on the results of network data analysis
simulations. Both the direct search and the confirmation of the supernova event
are considered. In addition, some physical studies following the discovery of a
supernova GW emission are also mentioned: from the absolute neutrino mass to
the supernova physics or the black hole signature, the potential spectrum of
discoveries is wide.Comment: Revised version, accepted for publication in Astroparticle Physic
Spatial methods for event reconstruction in CLEAN
In CLEAN (Cryogenic Low Energy Astrophysics with Noble gases), a proposed
neutrino and dark matter detector, background discrimination is possible if one
can determine the location of an ionizing radiation event with high accuracy.
We simulate ionizing radiation events that produce multiple scintillation
photons within a spherical detection volume filled with liquid neon. We
estimate the radial location of a particular ionizing radiation event based on
the observed count data corresponding to that event. The count data are
collected by detectors mounted at the spherical boundary of the detection
volume. We neglect absorption, but account for Rayleigh scattering. To account
for wavelength-shifting of the scintillation light, we assume that photons are
absorbed and re-emitted at the detectors. Here, we develop spatial Maximum
Likelihood methods for event reconstruction, and study their performance in
computer simulation experiments. We also study a method based on the centroid
of the observed count data. We calibrate our estimates based on training data
Time-frequency detection of Gravitational Waves
We present a time-frequency method to detect gravitational wave signals in
interferometric data. This robust method can detect signals from poorly modeled
and unmodeled sources. We evaluate the method on simulated data containing
noise and signal components. The noise component approximates initial LIGO
interferometer noise. The signal components have the time and frequency
characteristics postulated by Flanagan and Hughes for binary black hole
coalescence. The signals correspond to binaries with total masses between to and with (optimal filter) signal-to-noise ratios of 7
to 12. The method is implementable in real time, and achieves a coincident
false alarm rate for two detectors 1 per 475 years. At this false
alarm rate, the single detector false dismissal rate for our signal model is as
low as 5.3% at an SNR of 10. We expect to obtain similar or better detection
rates with this method for any signal of similar power that satisfies certain
adiabaticity criteria. Because optimal filtering requires knowledge of the
signal waveform to high precision, we argue that this method is likely to
detect signals that are undetectable by optimal filtering, which is at present
the best developed detection method for transient sources of gravitational
waves.Comment: 24 pages, 5 figures, uses REVTE
Gravitational waves: search results, data analysis and parameter estimation
The Amaldi 10 Parallel Session C2 on gravitational wave (GW) search results, data analysis and parameter estimation included three lively sessions of lectures by 13 presenters, and 34 posters. The talks and posters covered a huge range of material, including results and analysis techniques for ground-based GW detectors, targeting anticipated signals from different astrophysical sources: compact binary inspiral, merger and ringdown; GW bursts from intermediate mass binary black hole mergers, cosmic string cusps, core-collapse supernovae, and other unmodeled sources; continuous waves from spinning neutron stars; and a stochastic GW background. There was considerable emphasis on Bayesian techniques for estimating the parameters of coalescing compact binary systems from the gravitational waveforms extracted from the data from the advanced detector network. This included methods to distinguish deviations of the signals from what is expected in the context of General Relativity
Gravitational wave astronomy - astronomy of the 21st century
An enigmatic prediction of Einstein's general theory of relativity is
gravitational waves. With the observed decay in the orbit of the Hulse-Taylor
binary pulsar agreeing within a fraction of a percent with the theoretically
computed decay from Einstein's theory, the existence of gravitational waves was
firmly established. Currently there is a worldwide effort to detect
gravitational waves with interferometric gravitational wave observatories or
detectors and several such detectors have been built or being built. The
initial detectors have reached their design sensitivities and now the effort is
on to construct advanced detectors which are expected to detect gravitational
waves from astrophysical sources. The era of gravitational wave astronomy has
arrived. This article describes the worldwide effort which includes the effort
on the Indian front - the IndIGO project -, the principle underlying
interferometric detectors both on ground and in space, the principal noise
sources that plague such detectors, the astrophysical sources of gravitational
waves that one expects to detect by these detectors and some glimpse of the
data analysis methods involved in extracting the very weak gravitational wave
signals from detector noise.Comment: The contents of this article were finalised few months ago. The
discussion in the article pertains to the situation prevailing at that tim
Physics, Astrophysics and Cosmology with Gravitational Waves
Gravitational wave detectors are already operating at interesting sensitivity
levels, and they have an upgrade path that should result in secure detections
by 2014. We review the physics of gravitational waves, how they interact with
detectors (bars and interferometers), and how these detectors operate. We study
the most likely sources of gravitational waves and review the data analysis
methods that are used to extract their signals from detector noise. Then we
consider the consequences of gravitational wave detections and observations for
physics, astrophysics, and cosmology.Comment: 137 pages, 16 figures, Published version
<http://www.livingreviews.org/lrr-2009-2
Inferring the intensity of Poisson processes at the limit of the detector sensitivity (with a case study on gravitational wave burst search)
We consider the issue of reporting the result of search experiment in the
most unbiased and efficient way, i.e. in a way which allows an easy
interpretation and combination of results and which do not depend on whether
the experimenters believe or not to having found the searched-for effect. Since
this work uses the language of Bayesian theory, to which most physicists are
not used, we find that it could be useful to practitioners to have in a single
paper a simple presentation of Bayesian inference, together with an example of
application of it in search of rare processes.Comment: 36 pages, 11 figures, Latex files using cernart.cls (included). This
paper and related work are also available at
http://www-zeus.roma1.infn.it/~agostini/prob+stat.htm
Search method for long-duration gravitational-wave transients from neutron stars
We introduce a search method for a new class of gravitational-wave signals,
namely long-duration O(hours - weeks) transients from spinning neutron stars.
We discuss the astrophysical motivation from glitch relaxation models and we
derive a rough estimate for the maximal expected signal strength based on the
superfluid excess rotational energy. The transient signal model considered here
extends the traditional class of infinite-duration continuous-wave signals by a
finite start-time and duration. We derive a multi-detector Bayes factor for
these signals in Gaussian noise using \F-statistic amplitude priors, which
simplifies the detection statistic and allows for an efficient implementation.
We consider both a fully coherent statistic, which is computationally limited
to directed searches for known pulsars, and a cheaper semi-coherent variant,
suitable for wide parameter-space searches for transients from unknown neutron
stars. We have tested our method by Monte-Carlo simulation, and we find that it
outperforms orthodox maximum-likelihood approaches both in sensitivity and in
parameter-estimation quality.Comment: 20 pages, 9 figures; submitted to PR
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