122 research outputs found
Data from the LIGO I Science Run
The LIGO I Science Run is planned to begin in mid-2002. The characteristics of the data stream, data volumes, data products, and data availability are discussed. The data analysis activities will be undertaken by the LIGO Scientific Collaboration (LSC^2). These activities include operating dedicated on-site pipelines at the LIGO observatories. In addition, a dedicated off-site facility for will be dedicated to melding data from different interferometer datastreams (both LIGO and eventually those of other international projects as part of a network-wide analysis effort). Exploratory university-based research on LIGO data will likely be supported in part by the nascent US computing grid. LIGO Laboratory and the LSC are working on grid computing efforts within the GriPhyN (Grid Physics Network) collaboration research activities
XSIL: Extensible Scientific Interchange Language
We motivate and define the XSIL language as a flexible, hierarchical, extensible transport language for scientific data objects. The entire object may be represented in the file, or there may be metadata in the XSIL file, with a powerful, fault-tolerant linking mechanism to external data. The language is based on XML, and is designed not only for parsing and processing by machines, but also for presentation to humans through web browsers and web-database technology. There is a natural mapping between the elements of the XSIL language and the object model into which they are translated by the parser. As well as common objects (Parameter, Array, Time, Table), we have extended XSIL to include the IGWDFrame, used by gravitational-wave observatories
LIGO and the opening of a unique observational window on the universe
A unique window on the universe opened on September 14, 2015, with direct detection of gravitational waves by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors. This event culminated a half-century effort around the globe to develop terrestrial detectors of adequate sensitivity to achieve this goal. It also happened appropriately only a few months before the centennial of Einsteinâs final paper introducing the general theory of relativity. This detection provided the surprising discovery of a coalescing pair of âheavyâ black holes (more massive than â 25âM_àč) leading to the formation of a spinning â 62 solar mass black hole. One more binary black-hole detection and a significant candidate event demonstrated that a population of such merging binaries is formed in nature with a broad mass spectrum. This unique observational sample has already provided concrete measurements on the coalescence rates and has allowed us to test the theory of general relativity in the strong-field regime. As this nascent field of gravitational-wave astrophysics is emerging we are looking forward to the detection of binary mergers involving neutron stars and their electromagnetic counterparts, as well as continuous-wave sources, supernovae, a stochastic confusion background of compact-object mergers, known sources detected in unexpected ways, and completely unknown sources
Extended hierarchical search (EHS) algorithm for detection of gravitational waves from inspiraling compact binaries
Pattern matching techniques like matched filtering will be used for online
extraction of gravitational wave signals buried inside detector noise. This
involves cross correlating the detector output with hundreds of thousands of
templates spanning a multi-dimensional parameter space, which is very expensive
computationally. A faster implementation algorithm was devised by Mohanty and
Dhurandhar [1996] using a hierarchy of templates over the mass parameters,
which speeded up the procedure by about 25 to 30 times. We show that a further
reduction in computational cost is possible if we extend the hierarchy paradigm
to an extra parameter, namely, the time of arrival of the signal. In the first
stage, the chirp waveform is cut-off at a relatively low frequency allowing the
data to be coarsely sampled leading to cost saving in performing the FFTs. This
is possible because most of the signal power is at low frequencies, and
therefore the advantage due to hierarchy over masses is not compromised.
Results are obtained for spin-less templates up to the second post-Newtonian
(2PN) order for a single detector with LIGO I noise power spectral density. We
estimate that the gain in computational cost over a flat search is about 100.Comment: 6 pages, 6 EPS figures, uses CQG style iopart.cl
Plans for the LIGOâTAMA joint search for gravitational wave bursts
We describe the plans for a joint search for unmodelled gravitational wave bursts being carried out by the LIGO and TAMA Collaborations using data collected during FebruaryâApril 2003. We take a conservative approach to detection, requiring candidate gravitational wave bursts to be seen in coincidence by all four interferometers. We focus on some of the complications of performing this coincidence analysis, in particular the effects of the different alignments and noise spectra of the interferometers
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
Direct searches for a cosmological stochastic gravitational wave background
LIGO has completed a series of observations searching for evidence of a stochastic gravitational wave background. There has been no detection to date. However the sensitivity of the observations is approaching the Big Bang nucleosynthesis bound. Future observations will provide information that bounds a number of early Universe models of stochastic gravitational waves
A Virtual Data Grid for LIGO
GriPhyN (Grid Physics Network) is a large US collaboration to
build grid services for large physics experiments, one of which is LIGO, a
gravitational-wave observatory. This paper explains the physics and computing
challenges of LIGO, and the tools that GriPhyN will build to address
them. A key component needed to implement the data pipeline is a virtual
data service; a system to dynamically create data products requested during
the various stages. The data could possibly be already processed in a certain
way, it may be in a file on a storage system, it may be cached, or it may need
to be created through computation. The full elaboration of this system will al-low
complex data pipelines to be set up as virtual data objects, with existing
data being transformed in diverse ways
Optimal combination of signals from co-located gravitational wave interferometers for use in searches for a stochastic background
This article derives an optimal (i.e., unbiased, minimum variance) estimator
for the pseudo-detector strain for a pair of co-located gravitational wave
interferometers (such as the pair of LIGO interferometers at its Hanford
Observatory), allowing for possible instrumental correlations between the two
detectors. The technique is robust and does not involve any assumptions or
approximations regarding the relative strength of gravitational wave signals in
the detector pair with respect to other sources of correlated instrumental or
environmental noise. An expression is given for the effective power spectral
density of the combined noise in the pseudo-detector. This can then be
introduced into the standard optimal Wiener filter used to cross-correlate
detector data streams in order to obtain an optimal estimate of the stochastic
gravitational wave background. In addition, a dual to the optimal estimate of
strain is derived. This dual is constructed to contain no gravitational wave
signature and can thus be used as on "off-source" measurement to test
algorithms used in the "on-source" observation.Comment: 14 pages, 4 figures, submitted to Physical Review D Resubmitted after
editing paper in response to referee comments. Removed appendices A, B and
edited text accordingly. Improved legibility of figures. Corrected several
references. Corrected reference to science run number (S1 vs. S2) in text and
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