69 research outputs found
Searching for continuous gravitational wave signals using LIGO and Virgo detectors
Direct and unequivocal detection of gravitational waves represents a great
challenge of contemporary physics and astrophysics. A worldwide effort is
currently operating towards this direction, building ever sensitive detectors,
improving the modelling of gravitational wave sources and employing ever more
sophisticated and powerful data analysis techniques. In this paper we review
the current status of LIGO and Virgo ground based interferometric detectors and
some data analysis tools used in the continuous wave searches to extract the
faint gravitational signals from the interferometric noise data. Moreover we
discuss also relevant results from recent continuous wave searches.Comment: 9 pages, 1 figure, http://www.fisica.unisalento.it/iwra/index2.ph
First search for gravitational waves from the youngest known neutron star
We present a search for periodic gravitational waves from the neutron star in the supernova remnant Cassiopeia A. The search coherently analyzes data in a 12 day interval taken from the fifth science run of the Laser Interferometer Gravitational-Wave Observatory. It searches gravitational-wave frequencies from 100 to 300 Hz and covers a wide range of first and second frequency derivatives appropriate for the age of the remnant and for different spin-down mechanisms. No gravitational-wave signal was detected. Within the range of search frequencies, we set 95% confidence upper limits of (0.7-1.2) x 10(-24) on the intrinsic gravitational-wave strain, (0.4-4) x 10(-4) on the equatorial ellipticity of the neutron star, and 0.005-0.14 on the amplitude of r-mode oscillations of the neutron star. These direct upper limits beat indirect limits derived from energy conservation and enter the range of theoretical predictions involving crystalline exotic matter or runaway r-modes. This paper is also the first gravitational-wave search to present upper limits on the r-mode amplitude
Implementation and testing of the first prompt search for gravitational wave transients with electromagnetic counterparts
Aims. A transient astrophysical event observed in both gravitational wave (GW) and electromagnetic (EM) channels would yield rich scientific rewards. A first program initiating EM follow-ups to possible transient GW events has been developed and exercised by the LIGO and Virgo community in association with several partners. In this paper, we describe and evaluate the methods used to promptly identify and localize GW event candidates and to request images of targeted sky locations. Methods. During two observing periods (Dec. 17, 2009 to Jan. 8, 2010 and Sep. 2 to Oct. 20, 2010), a low-latency analysis pipeline was used to identify GW event candidates and to reconstruct maps of possible sky locations. A catalog of nearby galaxies and Milky Way globular clusters was used to select the most promising sky positions to be imaged, and this directional information was delivered to EM observatories with time lags of about thirty minutes. A Monte Carlo simulation has been used to evaluate the low-latency GW pipeline's ability to reconstruct source positions correctly. Results. For signals near the detection threshold, our low-latency algorithms often localized simulated GW burst signals to tens of square degrees, while neutron star/neutron star inspirals and neutron star/black hole inspirals were localized to a few hundred square degrees. Localization precision improves for moderately stronger signals. The correct sky location of signals well above threshold and originating from nearby galaxies may be observed with similar to 50% or better probability with a few pointings of wide-field telescopes
Search for gravitational waves from low mass compact binary coalescence in LIGO's sixth science run and Virgo's science runs 2 and 3
We report on a search for gravitational waves from coalescing compact binaries using LIGO and Virgo observations between July 7, 2009, and October 20, 2010. We searched for signals from binaries with total mass between 2 and 25M(circle dot); this includes binary neutron stars, binary black holes, and binaries consisting of a black hole and neutron star. The detectors were sensitive to systems up to 40 Mpc distant for binary neutron stars, and further for higher mass systems. No gravitational-wave signals were detected. We report upper limits on the rate of compact binary coalescence as a function of total mass, including the results from previous LIGO and Virgo observations. The cumulative 90% confidence rate upper limits of the binary coalescence of binary neutron star, neutron star-black hole, and binary black hole systems are 1.3 x 10(-4), 3.1 x 10(-5), and 6.4 x 10(-6) Mpc(-3) yr(-1), respectively. These upper limits are up to a factor 1.4 lower than previously derived limits. We also report on results from a blind injection challenge
A tapering window for time-domain templates and simulated signals in the detection of gravitational waves from coalescing compact binaries
Inspiral signals from binary black holes, in particular those with masses in
the range 10M_\odot \lsim M \lsim 1000 M_\odot, may last for only a few
cycles within a detector's most sensitive frequency band. The spectrum of a
square-windowed time-domain signal could contain unwanted power that can cause
problems in gravitational wave data analysis, particularly when the waveforms
are of short duration. There may be leakage of power into frequency bins where
no such power is expected, causing an excess of false alarms. We present a
method of tapering the time-domain waveforms that significantly reduces
unwanted leakage of power, leading to a spectrum that agrees very well with
that of a long duration signal. Our tapered window also decreases the false
alarms caused by instrumental and environmental transients that are picked up
by templates with spurious signal power. The suppression of background is an
important goal in noise-dominated searches and can lead to an improvement in
the detection efficiency of the search algorithms
A blind hierarchical coherent search for gravitational-wave signals from coalescing compact binaries in a network of interferometric detectors
We describe a hierarchical data analysis pipeline for coherently searching
for gravitational wave (GW) signals from non-spinning compact binary
coalescences (CBCs) in the data of multiple earth-based detectors. It assumes
no prior information on the sky position of the source or the time of
occurrence of its transient signals and, hence, is termed "blind". The pipeline
computes the coherent network search statistic that is optimal in stationary,
Gaussian noise, and allows for the computation of a suite of alternative
statistics and signal-based discriminators that can improve its performance in
real data. Unlike the coincident multi-detector search statistics employed so
far, the coherent statistics are different in the sense that they check for the
consistency of the signal amplitudes and phases in the different detectors with
their different orientations and with the signal arrival times in them. The
first stage of the hierarchical pipeline constructs coincidences of triggers
from the multiple interferometers, by requiring their proximity in time and
component masses. The second stage follows up on these coincident triggers by
computing the coherent statistics. The performance of the hierarchical coherent
pipeline on Gaussian data is shown to be better than the pipeline with just the
first (coincidence) stage.Comment: 12 pages, 3 figures, accepted for publication in Classical and
Quantum Gravit
An all-sky search algorithm for continuous gravitational waves from spinning neutron stars in binary systems
Rapidly spinning neutron stars with non-axisymmetric mass distributions are
expected to generate quasi-monochromatic continuous gravitational waves. While
many searches for unknown, isolated spinning neutron stars have been carried
out, there have been no previous searches for unknown sources in binary
systems. Since current search methods for unknown, isolated neutron stars are
already computationally limited, expanding the parameter space searched to
include binary systems is a formidable challenge. We present a new hierarchical
binary search method called TwoSpect, which exploits the periodic orbital
modulations of the continuous waves by searching for patterns in doubly
Fourier-transformed data. We will describe the TwoSpect search pipeline,
including its mitigation of detector noise variations and corrections for
Doppler frequency modulation caused by changing detector velocity. Tests on
Gaussian noise and on a set of simulated signals will be presented.Comment: 22 pages, 10 figures, 1 table, Submitted to Classical and Quantum
Gravit
The Critical Coupling Likelihood Method: A new approach for seamless integration of environmental and operating conditions of gravitational wave detectors into gravitational wave searches
Any search effort for gravitational waves (GW) using interferometric
detectors like LIGO needs to be able to identify if and when noise is coupling
into the detector's output signal. The Critical Coupling Likelihood (CCL)
method has been developed to characterize potential noise coupling and in the
future aid GW search efforts. By testing two hypotheses about pairs of
channels, CCL is able to identify undesirable coupled instrumental noise from
potential GW candidates. Our preliminary results show that CCL can associate up
to of observed artifacts with , to local noise sources,
while reducing the duty cycle of the instrument by . An approach
like CCL will become increasingly important as GW research moves into the
Advanced LIGO era, going from the first GW detection to GW astronomy.Comment: submitted CQ
Reducing the effect of seismic noise in LIGO searches by targeted veto generation
The Laser Interferometer Gravitational-Wave Observatory forms part of the
international effort to detect and study gravitational waves of astrophysical
origin. One of the major obstacles for this project with the first generation
detectors was the effect of seismic noise on instrument sensitivity -
environmental disturbances causing motion of the interferometer optics,
coupling as noise in the gravitational wave data output. Typically transient
noise events have been identified by finding coincidence between noise in an
auxiliary data signal (with negligible sensitivity to gravitational waves) and
noise in the gravitational wave data, but attempts to include seismometer
readings in this scheme have proven ineffective. We present a new method of
generating a list of times of high seismic noise by tuning a gravitational wave
burst detection pipeline to the low frequency signature of these events. This
method has proven very effective at removing transients of seismic origin from
the gravitational wave (GW) data with only a small loss of analysable time. We
also present an outline for extending this method to other noise sources.Comment: 16 pages, 5 figure
Astronomy and astrophysics with gravitational waves in the Advanced Detector Era
With the advanced gravitational wave detectors coming on line in the next 5
years, we expect to make the first detections of gravitational waves from
astrophysical sources, and study the properties of the waves themselves as
tests of General Relativity. In addition, these gravitational waves will be
powerful tools for the study of their astrophysical sources and source
populations. They carry information that is quite complementary to what can be
learned from electromagnetic or neutrino observations, probing the central
gravitational engines that power the electromagnetic emissions. Preparations
are being made to enable near-simultaneous observations of both gravitational
wave and electromagnetic observations of transient sources, using low-latency
search pipelines and rapid sky localization. We will review the many
opportunities for multi-messenger astronomy and astrophysics with gravitational
waves enabled by the advanced detectors, and the preparations that are being
made to quickly and fully exploit them.Comment: 10 pages, no figures. Submitted to the proceedings of the 9th Edoardo
Amaldi Conference on Gravitational Waves, and the 2011 Numerical Relativity -
Data Analysis (NRDA) meeting, held 10-15 July 2011 in Cardiff, Wales, UK,
July 10-15 2011 (Special issue of CQG). Updated in response to CQG referees
and CQG proofs. Accepted by CQ
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