5,980 research outputs found
Robust statistics for deterministic and stochastic gravitational waves in non-Gaussian noise I: Frequentist analyses
Gravitational wave detectors will need optimal signal-processing algorithms
to extract weak signals from the detector noise. Most algorithms designed to
date are based on the unrealistic assumption that the detector noise may be
modeled as a stationary Gaussian process. However most experiments exhibit a
non-Gaussian ``tail'' in the probability distribution. This ``excess'' of large
signals can be a troublesome source of false alarms. This article derives an
optimal (in the Neyman-Pearson sense, for weak signals) signal processing
strategy when the detector noise is non-Gaussian and exhibits tail terms. This
strategy is robust, meaning that it is close to optimal for Gaussian noise but
far less sensitive than conventional methods to the excess large events that
form the tail of the distribution. The method is analyzed for two different
signal analysis problems: (i) a known waveform (e.g., a binary inspiral chirp)
and (ii) a stochastic background, which requires a multi-detector signal
processing algorithm. The methods should be easy to implement: they amount to
truncation or clipping of sample values which lie in the outlier part of the
probability distribution.Comment: RevTeX 4, 17 pages, 8 figures, typos corrected from first version
Enabling high confidence detections of gravitational-wave bursts
With the advanced LIGO and Virgo detectors taking observations the detection
of gravitational waves is expected within the next few years. Extracting
astrophysical information from gravitational wave detections is a well-posed
problem and thoroughly studied when detailed models for the waveforms are
available. However, one motivation for the field of gravitational wave
astronomy is the potential for new discoveries. Recognizing and characterizing
unanticipated signals requires data analysis techniques which do not depend on
theoretical predictions for the gravitational waveform. Past searches for
short-duration un-modeled gravitational wave signals have been hampered by
transient noise artifacts, or "glitches," in the detectors. In some cases, even
high signal-to-noise simulated astrophysical signals have proven difficult to
distinguish from glitches, so that essentially any plausible signal could be
detected with at most 2-3 level confidence. We have put forth the
BayesWave algorithm to differentiate between generic gravitational wave
transients and glitches, and to provide robust waveform reconstruction and
characterization of the astrophysical signals. Here we study BayesWave's
capabilities for rejecting glitches while assigning high confidence to
detection candidates through analytic approximations to the Bayesian evidence.
Analytic results are tested with numerical experiments by adding simulated
gravitational wave transient signals to LIGO data collected between 2009 and
2010 and found to be in good agreement.Comment: 15 pages, 6 figures, submitted to PR
Comparison of filters for detecting gravitational wave bursts in interferometric detectors
Filters developed in order to detect short bursts of gravitational waves in
interferometric detector outputs are compared according to three main points.
Conventional Receiver Operating Characteristics (ROC) are first built for all
the considered filters and for three typical burst signals. Optimized ROC are
shown for a simple pulse signal in order to estimate the best detection
efficiency of the filters in the ideal case, while realistic ones obtained with
filters working with several ``templates'' show how detection efficiencies can
be degraded in a practical implementation. Secondly, estimations of biases and
statistical errors on the reconstruction of the time of arrival of pulse-like
signals are then given for each filter. Such results are crucial for future
coincidence studies between Gravitational Wave detectors but also with neutrino
or optical detectors. As most of the filters require a pre-whitening of the
detector noise, the sensitivity to a non perfect noise whitening procedure is
finally analysed. For this purpose lines of various frequencies and amplitudes
are added to a Gaussian white noise and the outputs of the filters are studied
in order to monitor the excess of false alarms induced by the lines. The
comparison of the performances of the different filters finally show that they
are complementary rather than competitive.Comment: 32 pages (14 figures), accepted for publication in Phys. Rev.
Data analysis challenges in transient gravitational-wave astronomy
Gravitational waves are radiative solutions of space-time dynamics predicted
by Einstein's theory of General Relativity. A world-wide array of large-scale
and highly sensitive interferometric detectors constantly scrutinizes the
geometry of the local space-time with the hope to detect deviations that would
signal an impinging gravitational wave from a remote astrophysical source.
Finding the rare and weak signature of gravitational waves buried in
non-stationary and non-Gaussian instrument noise is a particularly challenging
problem. We will give an overview of the data-analysis techniques and
associated observational results obtained so far by Virgo (in Europe) and LIGO
(in the US), along with the prospects offered by the up-coming advanced
versions of those detectors.Comment: 7 pages, 5 figures, Proceedings of the ARENA'12 Conference, few minor
change
The NANOGrav 11 yr Data Set: Limits on Gravitational Wave Memory
The mergers of supermassive black hole binaries (SMBHBs) promise to be incredible sources of gravitational waves (GWs). While the oscillatory part of the merger gravitational waveform will be outside the frequency sensitivity range of pulsar timing arrays, the nonoscillatory GW memory effect is detectable. Further, any burst of GWs will produce GW memory, making memory a useful probe of unmodeled exotic sources and new physics. We searched the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) 11 yr data set for GW memory. This data set is sensitive to very low-frequency GWs of ~3 to 400 nHz (periods of ~11 yr–1 month). Finding no evidence for GWs, we placed limits on the strain amplitude of GW memory events during the observation period. We then used the strain upper limits to place limits on the rate of GW memory causing events. At a strain of 2.5 × 10⁻¹⁴, corresponding to the median upper limit as a function of source sky position, we set a limit on the rate of GW memory events at <0.4 yr⁻¹. That strain corresponds to an SMBHB merger with reduced mass of ηM ~ 2 × 10¹⁰ M_⊙ and inclination of ι = π/3 at a distance of 1 Gpc. As a test of our analysis, we analyzed the NANOGrav 9 yr data set as well. This analysis found an anomolous signal, which does not appear in the 11 yr data set. This signal is not a GW, and its origin remains unknown
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