32,400 research outputs found
Aperture synthesis for gravitational-wave data analysis: Deterministic Sources
Gravitational wave detectors now under construction are sensitive to the
phase of the incident gravitational waves. Correspondingly, the signals from
the different detectors can be combined, in the analysis, to simulate a single
detector of greater amplitude and directional sensitivity: in short, aperture
synthesis. Here we consider the problem of aperture synthesis in the special
case of a search for a source whose waveform is known in detail: \textit{e.g.,}
compact binary inspiral. We derive the likelihood function for joint output of
several detectors as a function of the parameters that describe the signal and
find the optimal matched filter for the detection of the known signal. Our
results allow for the presence of noise that is correlated between the several
detectors. While their derivation is specialized to the case of Gaussian noise
we show that the results obtained are, in fact, appropriate in a well-defined,
information-theoretic sense even when the noise is non-Gaussian in character.
The analysis described here stands in distinction to ``coincidence
analyses'', wherein the data from each of several detectors is studied in
isolation to produce a list of candidate events, which are then compared to
search for coincidences that might indicate common origin in a gravitational
wave signal. We compare these two analyses --- optimal filtering and
coincidence --- in a series of numerical examples, showing that the optimal
filtering analysis always yields a greater detection efficiency for given false
alarm rate, even when the detector noise is strongly non-Gaussian.Comment: 39 pages, 4 figures, submitted to Phys. Rev.
Robust Gravitational Wave Burst Detection and Source Localization in a Network of Interferometers Using Cross Wigner Spectra
We discuss a fast cross-Wigner transform based technique for detecting
gravitational wave bursts, and estimating the direction of arrival, using a
network of (three) non co-located interferometric detectors. The performances
of the detector as a function of signal strength and source location, and the
accuracy of the direction of arrival estimation are investigated by numerical
simulations.Comment: accepted in Class. Quantum Gravit
Search strategies for long gravitational-wave transients: hidden Markov model tracking and seedless clustering
A number of detections have been made in the past few years of gravitational
waves from compact binary coalescences. While there exist well-understood
waveform models for signals from compact binary coalescences, many sources of
gravitational waves are not well modeled, including potential long-transient
signals from a binary neutron star post-merger remnant. Searching for these
sources requires robust detection algorithms that make minimal assumptions
about any potential signals. In this paper, we compare two unmodeled search
schemes for long-transient gravitational waves, operating on cross-power
spectrograms. One is an efficient algorithm first implemented for continuous
wave searches, based on a hidden Markov model. The other is a seedless
clustering method, which has been used in transient gravitational wave analysis
in the past. We quantify the performance of both algorithms, including
sensitivity and computational cost, by simulating synthetic signals with a
special focus on sources like binary neutron star post-merger remnants. We
demonstrate that the hidden Markov model tracking is a good option in
model-agnostic searches for low signal-to-noise ratio signals. We also show
that it can outperform the seedless method for certain categories of signals
while also being computationally more efficient.Comment: 10 pages, 7 figure
Optimal detection of burst events in gravitational wave interferometric observatories
We consider the problem of detecting a burst signal of unknown shape. We
introduce a statistic which generalizes the excess power statistic proposed by
Flanagan and Hughes and extended by Anderson et al. The statistic we propose is
shown to be optimal for arbitrary noise spectral characteristic, under the two
hypotheses that the noise is Gaussian, and that the prior for the signal is
uniform. The statistic derivation is based on the assumption that a signal
affects only affects N samples in the data stream, but that no other
information is a priori available, and that the value of the signal at each
sample can be arbitrary. We show that the proposed statistic can be implemented
combining standard time-series analysis tools which can be efficiently
implemented, and the resulting computational cost is still compatible with an
on-line analysis of interferometric data. We generalize this version of an
excess power statistic to the multiple detector case, also including the effect
of correlated noise. We give full details about the implementation of the
algorithm, both for the single and the multiple detector case, and we discuss
exact and approximate forms, depending on the specific characteristics of the
noise and on the assumed length of the burst event. As a example, we show what
would be the sensitivity of the network of interferometers to a delta-function
burst.Comment: 21 pages, 5 figures in 3 groups. Submitted for publication to
Phys.Rev.D. A Mathematica notebook is available at
http://www.ligo.caltech.edu/~avicere/nda/burst/Burst.nb which allows to
reproduce the numerical results of the pape
Likelihood-ratio ranking of gravitational-wave candidates in a non-Gaussian background
We describe a general approach to detection of transient gravitational-wave
signals in the presence of non-Gaussian background noise. We prove that under
quite general conditions, the ratio of the likelihood of observed data to
contain a signal to the likelihood of it being a noise fluctuation provides
optimal ranking for the candidate events found in an experiment. The
likelihood-ratio ranking allows us to combine different kinds of data into a
single analysis. We apply the general framework to the problem of unifying the
results of independent experiments and the problem of accounting for
non-Gaussian artifacts in the searches for gravitational waves from compact
binary coalescence in LIGO data. We show analytically and confirm through
simulations that in both cases the likelihood ratio statistic results in an
improved analysis.Comment: 10 pages, 6 figure
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
Detection of gravitational wave bursts by interferometric detectors
We study in this paper some filters for the detection of burst-like signals
in the data of interferometric gravitational-wave detectors. We present first
two general (non-linear) filters with no {\it a priori} assumption on the
waveforms to detect. A third filter, a peak correlator, is also introduced and
permits to estimate the gain, when some prior information is known about the
waveforms. We use the catalogue of supernova gravitational-wave signals built
by Zwerger and M\"uller in order to have a benchmark of the performance of each
filter and to compare to the performance of the optimal filter. The three
filters could be a part of an on-line triggering in interferometric
gravitational-wave detectors, specialised in the selection of burst events.Comment: 15 pages, 8 figure
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