1,286 research outputs found
Testing the normality of the gravitational wave data with a low cost recursive estimate of the kurtosis
We propose a monitoring indicator of the normality of the output of a
gravitational wave detector. This indicator is based on the estimation of the
kurtosis (i.e., the 4th order statistical moment normalized by the variance
squared) of the data selected in a time sliding window. We show how a low cost
(because recursive) implementation of such estimation is possible and we
illustrate the validity of the presented approach with a few examples using
simulated random noises.Comment: 4 pages, 3 figures. In the Proceedings of the 3rd workshop on Physics
in Signal and Image Processing (Grenoble), 200
Adaptive filtering techniques for interferometric data preparation: removal of long-term sinusoidal signals and oscillatory transients
We propose an adaptive denoising scheme for poorly modeled non-Gaussian
features in the gravitational wave interferometric data. Preliminary tests on
real data show encouraging results.Comment: 4 pages, 2 figures. Proceedings of GWDAW99 (Roma, Dec. 1999), to
appear in Int. J. Mod. Phys.
Best chirplet chain: near-optimal detection of gravitational wave chirps
The list of putative sources of gravitational waves possibly detected by the
ongoing worldwide network of large scale interferometers has been continuously
growing in the last years. For some of them, the detection is made difficult by
the lack of a complete information about the expected signal. We concentrate on
the case where the expected GW is a quasi-periodic frequency modulated signal
i.e., a chirp. In this article, we address the question of detecting an a
priori unknown GW chirp. We introduce a general chirp model and claim that it
includes all physically realistic GW chirps. We produce a finite grid of
template waveforms which samples the resulting set of possible chirps. If we
follow the classical approach (used for the detection of inspiralling binary
chirps, for instance), we would build a bank of quadrature matched filters
comparing the data to each of the templates of this grid. The detection would
then be achieved by thresholding the output, the maximum giving the individual
which best fits the data. In the present case, this exhaustive search is not
tractable because of the very large number of templates in the grid. We show
that the exhaustive search can be reformulated (using approximations) as a
pattern search in the time-frequency plane. This motivates an approximate but
feasible alternative solution which is clearly linked to the optimal one.
[abridged version of the abstract]Comment: 23 pages, 9 figures. Accepted for publication in Phys. Rev D Some
typos corrected and changes made according to referee's comment
Uncertainty and Spectrogram Geometry
International audienceUltimate possibilities of localization for time-frequency representations are first reviewed from a joint perspective, evidencing that Heisenberg-type pointwise limits are not exclusive of sharp localization along trajectories in the plane. Spectrogram reassignment offers such a possibility and, in order to revisit its connection with uncertainty, geometrical properties of spectrograms are statistically investigated in the generic case of white Gaussian noise. Based on Voronoi tessellations and Delaunay triangulations attached to extrema, it is shown that, in a first approximation, local energy ''patches'' are distributed according to a randomized hexagonal lattice with a typical scale within a factor of a few that of minimum uncertainty Gabor logons
Making Reassignment Adjustable: the Levenberg-Marquardt Approach
accepted for publication, to appear in Proc. of IEEE Int. Conf. on Acoust., Speech and Signal Proc. ICASSP-12, Kyoto (Japan), March 25-30, 2012.International audienceThis paper presents a new time-frequency reassignment process of the spectrogram, called the Levenberg-Marquardt reassignment. Compared to the classical one, this new reassignment process uses the second-order derivatives of the phase of the short-time Fourier transform, and provides the user with a setting parameter. This parameter allows him to produce either a weaker or a stronger localization of the signal components in the time-frequency plane
Power filters for gravitational wave bursts: network operation for source position estimation
A method is presented to generalize the power detectors for short bursts of
gravitational waves that have been developed for single interferometers so that
they can optimally process data from a network of interferometers. The
performances of this method for the estimation of the position of the source
are studied using numerical simulations.Comment: To appear in the proceedings of GWDAW 2002 (Classical and Quantum
Gravity, Special issue
A learning approach to the detection of gravitational wave transients
We investigate the class of quadratic detectors (i.e., the statistic is a
bilinear function of the data) for the detection of poorly modeled
gravitational transients of short duration. We point out that all such
detection methods are equivalent to passing the signal through a filter bank
and linearly combine the output energy. Existing methods for the choice of the
filter bank and of the weight parameters rely essentially on the two following
ideas: (i) the use of the likelihood function based on a (possibly
non-informative) statistical model of the signal and the noise, (ii) the use of
Monte-Carlo simulations for the tuning of parametric filters to get the best
detection probability keeping fixed the false alarm rate. We propose a third
approach according to which the filter bank is "learned" from a set of training
data. By-products of this viewpoint are that, contrarily to previous methods,
(i) there is no requirement of an explicit description of the probability
density function of the data when the signal is present and (ii) the filters we
use are non-parametric. The learning procedure may be described as a two step
process: first, estimate the mean and covariance of the signal with the
training data; second, find the filters which maximize a contrast criterion
referred to as deflection between the "noise only" and "signal+noise"
hypothesis. The deflection is homogeneous to the signal-to-noise ratio and it
uses the quantities estimated at the first step. We apply this original method
to the problem of the detection of supernovae core collapses. We use the
catalog of waveforms provided recently by Dimmelmeier et al. to train our
algorithm. We expect such detector to have better performances on this
particular problem provided that the reference signals are reliable.Comment: 22 pages, 4 figure
The Antares Neutrino Telescope and Multi-Messenger Astronomy
Antares is currently the largest neutrino telescope operating in the Northern
Hemisphere, aiming at the detection of high-energy neutrinos from astrophysical
sources. Such observations would provide important clues about the processes at
work in those sources, and possibly help solve the puzzle of ultra-high energy
cosmic rays. In this context, Antares is developing several programs to improve
its capabilities of revealing possible spatial and/or temporal correlations of
neutrinos with other cosmic messengers: photons, cosmic rays and gravitational
waves. The neutrino telescope and its most recent results are presented,
together with these multi-messenger programs.Comment: 10 pages, 7 figures. Proceedings of the 14th Gravitational Wave Data
Analysis Workshop (GWDAW-14) in Roma - January 26th-29th, 201
Short GRBs at the dawn of the gravitational wave era
We derive the luminosity function and redshift distribution of short Gamma
Ray Bursts (SGRBs) using (i) all the available observer-frame constraints (i.e.
peak flux, fluence, peak energy and duration distributions) of the large
population of Fermi SGRBs and (ii) the rest-frame properties of a complete
sample of Swift SGRBs. We show that a steep with a>2.0
is excluded if the full set of constraints is considered. We implement a Monte
Carlo Markov Chain method to derive the and functions
assuming intrinsic Ep-Liso and Ep-Eiso correlations or independent
distributions of intrinsic peak energy, luminosity and duration. To make our
results independent from assumptions on the progenitor (NS-NS binary mergers or
other channels) and from uncertainties on the star formation history, we assume
a parametric form for the redshift distribution of SGRBs. We find that a
relatively flat luminosity function with slope ~0.5 below a characteristic
break luminosity ~3 erg/s and a redshift distribution of SGRBs
peaking at z~1.5-2 satisfy all our constraints. These results hold also if no
Ep-Liso and Ep-Eiso correlations are assumed. We estimate that, within ~200 Mpc
(i.e. the design aLIGO range for the detection of GW produced by NS-NS merger
events), 0.007-0.03 SGRBs yr should be detectable as gamma-ray events.
Assuming current estimates of NS-NS merger rates and that all NS-NS mergers
lead to a SGRB event, we derive a conservative estimate of the average opening
angle of SGRBs: ~3-6 deg. Our luminosity function implies an
average luminosity L~1.5 erg/s, nearly two orders of magnitude
higher than previous findings, which greatly enhances the chance of observing
SGRB "orphan" afterglows. Efforts should go in the direction of finding and
identifying such orphan afterglows as counterparts of GW events.Comment: 13 pages, 5 figures, 2 tables. Accepted for publication in Astronomy
& Astrophysics. Figure 5 and angle ranges corrected in revised versio
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