17 research outputs found
The search for gravitational wave bursts in data from the second LIGO science run
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.Includes bibliographical references (p. 279-293).The network of detectors comprising the Laser Interferometer Gravitational-wave Observatory (LIGO) are among a new generation of detectors that seek to make the first direct observation of gravitational waves. While providing strong support for the General Theory of Relativity, such observations will also permit new tests of physical theory in regions of strong space-time curvature and high matter-energy density. However, the observed signals are expected to occur near the limit of detector sensitivity. The problem of identifying such small signals is the primary focus of this work. This work presents a novel method for the identification of astrophysically unmodeled bursts of gravitational radiation in data from networks of interferometric detectors. The method is based on the Q transform, a multiresolution time-frequency transform that efficiently targets waveforms within a finite region of time, frequency, and Q space. The method is also based on a modification of linear prediction that greatly simplifies the resulting statistical analysis by whitening interferometric detector data prior to Q transform analysis. Together, these techniques form the basis of a complete analysis pipeline that is equivalent to a template-based matched filter search for minimum uncertainty waveforms in the whitened data stream. This method is then applied to search for gravitational-wave bursts with duration less than 1 second and frequency content between 64 and 1024 Hz in coincident data from two detectors during second LIGO science run. Although no gravitational-wave bursts are identified,(cont.) upper bounds are reported for the rate of gravitational-wave bursts as a function of signal strength for isotropic and galactic populations of sources with both abstract and astrophysically motivated waveform. The results indicate a maximum of 0.09 events per day at the 90% confidence level for bursts with characteristic strain amplitude in excess of 10-20 to 10-19 strain Hz-l/2 depending on waveform. A comparison with previous searches demonstrates that this search is one of the most sensitive to date for gravitational-wave bursts of unknown waveform, and is inconsistent with recent indications for an statistical excess of events by the ROG collaboration at above the 99% confidence level.by Shourov Keith Chatterji.Ph.D
Coherent network analysis technique for discriminating gravitational-wave bursts from instrumental noise
Existing coherent network analysis techniques for detecting
gravitational-wave bursts simultaneously test data from multiple observatories
for consistency with the expected properties of the signals. These techniques
assume the output of the detector network to be the sum of a stationary
Gaussian noise process and a gravitational-wave signal, and they may fail in
the presence of transient non-stationarities, which are common in real
detectors. In order to address this problem we introduce a consistency test
that is robust against noise non-stationarities and allows one to distinguish
between gravitational-wave bursts and noise transients. This technique does not
require any a priori knowledge of the putative burst waveform.Comment: 18 pages, 11 figures; corrected corrupted figur
X-Pipeline: An analysis package for autonomous gravitational-wave burst searches
Autonomous gravitational-wave searches -- fully automated analyses of data
that run without human intervention or assistance -- are desirable for a number
of reasons. They are necessary for the rapid identification of
gravitational-wave burst candidates, which in turn will allow for follow-up
observations by other observatories and the maximum exploitation of their
scientific potential. A fully automated analysis would also circumvent the
traditional "by hand" setup and tuning of burst searches that is both
labourious and time consuming. We demonstrate a fully automated search with
X-Pipeline, a software package for the coherent analysis of data from networks
of interferometers for detecting bursts associated with GRBs and other
astrophysical triggers. We discuss the methods X-Pipeline uses for automated
running, including background estimation, efficiency studies, unbiased optimal
tuning of search thresholds, and prediction of upper limits. These are all done
automatically via Monte Carlo with multiple independent data samples, and
without requiring human intervention. As a demonstration of the power of this
approach, we apply X-Pipeline to LIGO data to search for gravitational-wave
emission associated with GRB 031108. We find that X-Pipeline is sensitive to
signals approximately a factor of 2 weaker in amplitude than those detectable
by the cross-correlation technique used in LIGO searches to date. We conclude
with the prospects for running X-Pipeline as a fully autonomous, near real-time
triggered burst search in the next LSC-Virgo Science Run.Comment: 18 pages, 10 figures. Minor edits and clarifications; added more
background on gravitational waves and detectors. To appear in New Journal of
Physics
Testing gravitational-wave searches with numerical relativity waveforms: Results from the first Numerical INJection Analysis (NINJA) project
The Numerical INJection Analysis (NINJA) project is a collaborative effort between members of the numerical relativity and gravitational-wave data analysis communities. The purpose of NINJA is to study the sensitivity of existing gravitational-wave search algorithms using numerically generated waveforms and to foster closer collaboration between the numerical relativity and data analysis communities. We describe the results of the first NINJA analysis which focused on gravitational waveforms from binary black hole coalescence. Ten numerical relativity groups contributed numerical data which were used to generate a set of gravitational-wave signals. These signals were injected into a simulated data set, designed to mimic the response of the initial LIGO and Virgo gravitational-wave detectors. Nine groups analysed this data using search and parameter-estimation pipelines. Matched filter algorithms, un-modelled-burst searches and Bayesian parameter estimation and model-selection algorithms were applied to the data. We report the efficiency of these search methods in detecting the numerical waveforms and measuring their parameters. We describe preliminary comparisons between the different search methods and suggest improvements for future NINJA analyses. © 2009 IOP Publishing Ltd
Status of NINJA: The Numerical INJection Analysis project
The 2008 NRDA conference introduced the Numerical INJection Analysis project (NINJA), a new collaborative effort between the numerical relativity community and the data analysis community. NINJA focuses on modeling and searching for gravitational wave signatures from the coalescence of binary system of compact objects. We review the scope of this collaboration and the components of the first NINJA project, where numerical relativity groups, shared waveforms and data analysis teams applied various techniques to detect them when embedded in colored Gaussian noise. © 2009 IOP Publishing Ltd
Testing gravitational-wave searches with numerical relativity waveforms: Results from the first Numerical INJection Analysis (NINJA) project
The Numerical INJection Analysis (NINJA) project is a collaborative effort
between members of the numerical relativity and gravitational-wave data
analysis communities. The purpose of NINJA is to study the sensitivity of
existing gravitational-wave search algorithms using numerically generated
waveforms and to foster closer collaboration between the numerical relativity
and data analysis communities. We describe the results of the first NINJA
analysis which focused on gravitational waveforms from binary black hole
coalescence. Ten numerical relativity groups contributed numerical data which
were used to generate a set of gravitational-wave signals. These signals were
injected into a simulated data set, designed to mimic the response of the
Initial LIGO and Virgo gravitational-wave detectors. Nine groups analysed this
data using search and parameter-estimation pipelines. Matched filter
algorithms, un-modelled-burst searches and Bayesian parameter-estimation and
model-selection algorithms were applied to the data. We report the efficiency
of these search methods in detecting the numerical waveforms and measuring
their parameters. We describe preliminary comparisons between the different
search methods and suggest improvements for future NINJA analyses.Comment: 56 pages, 25 figures; various clarifications; accepted to CQ
Unmodeled search for black hole binary systems in the NINJA project
The gravitational-wave signature from binary black hole coalescences is an important target for ground-based interferometric detectors such as LIGO and Virgo. The Numerical INJection Analysis (NINJA) project brought together the numerical relativity and gravitational wave data analysis communities, with the goal to optimize the detectability of these events. In its first instantiation, the NINJA project produced a simulated data set with numerical waveforms from binary black hole coalescences of various morphologies (spin, mass ratio, initial conditions), superimposed to Gaussian colored noise at the design sensitivity for initial LIGO and Virgo. We analyzed the NINJA simulated data set with the Q-pipeline algorithm, designed for the all-sky detection of gravitational-wave bursts with minimal assumptions on the shape of the waveform. The algorithm filters the data with a bank of sine-Gaussians, sinusoids with Gaussian envelope, to identify significant excess power in the time-frequency domain. We compared the performance of this burst search algorithm with lalapps_ring, which match-filters data with a bank of ring-down templates to specifically target the final stage of a coalescence of black holes. A comparison of the output of the two algorithms on NINJA data in a single detector analysis yielded qualitatively consistent results; however, due to the low simulation statistics in the first NINJA project, it is premature to draw quantitative conclusions at this stage, and further studies with higher statistics and real detector noise will be needed