224 research outputs found
Searching for Galactic White Dwarf Binaries in Mock LISA Data using an F-Statistic Template Bank
We describe an F-statistic search for continuous gravitational waves from
galactic white-dwarf binaries in simulated LISA Data. Our search method employs
a hierarchical template-grid based exploration of the parameter space. In the
first stage, candidate sources are identified in searches using different
simulated laser signal combinations (known as TDI variables). Since each source
generates a primary maximum near its true "Doppler parameters" (intrinsic
frequency and sky position) as well as numerous secondary maxima of the
F-statistic in Doppler parameter space, a search for multiple sources needs to
distinguish between true signals and secondary maxima associated with other,
"louder" signals. Our method does this by applying a coincidence test to reject
candidates which are not found at nearby parameter space positions in searches
using each of the three TDI variables. For signals surviving the coincidence
test, we perform a fully coherent search over a refined parameter grid to
provide an accurate parameter estimation for the final candidates. Suitably
tuned, the pipeline is able to extract 1989 true signals with only 5 false
alarms. The use of the rigid adiabatic approximation allows recovery of signal
parameters with errors comparable to statistical expectations, although there
is still some systematic excess with respect to statistical errors expected
from Gaussian noise. An experimental iterative pipeline with seven rounds of
signal subtraction and re-analysis of the residuals allows us to increase the
number of signals recovered to a total of 3419 with 29 false alarms.Comment: 29 pages, 11 figures; submitted to Classical and Quantum Gravit
Targeted search for continuous gravitational waves: Bayesian versus maximum-likelihood statistics
We investigate the Bayesian framework for detection of continuous
gravitational waves (GWs) in the context of targeted searches, where the phase
evolution of the GW signal is assumed to be known, while the four amplitude
parameters are unknown. We show that the orthodox maximum-likelihood statistic
(known as F-statistic) can be rediscovered as a Bayes factor with an unphysical
prior in amplitude parameter space. We introduce an alternative detection
statistic ("B-statistic") using the Bayes factor with a more natural amplitude
prior, namely an isotropic probability distribution for the orientation of GW
sources. Monte-Carlo simulations of targeted searches show that the resulting
Bayesian B-statistic is more powerful in the Neyman-Pearson sense (i.e. has a
higher expected detection probability at equal false-alarm probability) than
the frequentist F-statistic.Comment: 12 pages, presented at GWDAW13, to appear in CQ
The Mock LISA Data Challenges: from Challenge 3 to Challenge 4
The Mock LISA Data Challenges are a program to demonstrate LISA data-analysis
capabilities and to encourage their development. Each round of challenges
consists of one or more datasets containing simulated instrument noise and
gravitational waves from sources of undisclosed parameters. Participants
analyze the datasets and report best-fit solutions for the source parameters.
Here we present the results of the third challenge, issued in Apr 2008, which
demonstrated the positive recovery of signals from chirping Galactic binaries,
from spinning supermassive--black-hole binaries (with optimal SNRs between ~ 10
and 2000), from simultaneous extreme-mass-ratio inspirals (SNRs of 10-50), from
cosmic-string-cusp bursts (SNRs of 10-100), and from a relatively loud
isotropic background with Omega_gw(f) ~ 10^-11, slightly below the LISA
instrument noise.Comment: 12 pages, 2 figures, proceedings of the 8th Edoardo Amaldi Conference
on Gravitational Waves, New York, June 21-26, 200
Studying stellar binary systems with the Laser Interferometer Space Antenna using Delayed Rejection Markov chain Monte Carlo methods
Bayesian analysis of LISA data sets based on Markov chain Monte Carlo methods
has been shown to be a challenging problem, in part due to the complicated
structure of the likelihood function consisting of several isolated local
maxima that dramatically reduces the efficiency of the sampling techniques.
Here we introduce a new fully Markovian algorithm, a Delayed Rejection
Metropolis-Hastings Markov chain Monte Carlo method, to efficiently explore
these kind of structures and we demonstrate its performance on selected LISA
data sets containing a known number of stellar-mass binary signals embedded in
Gaussian stationary noise.Comment: 12 pages, 4 figures, accepted in CQG (GWDAW-13 proceedings
A hierarchical search for gravitational waves from supermassive black hole binary mergers
We present a method to search for gravitational waves from coalescing
supermassive binary black holes in LISA data. The search utilizes the
-statistic to maximize over, and determine the values of, the
extrinsic parameters of the binary system. The intrinsic parameters are
searched over hierarchically using stochastically generated multi-dimensional
template banks to recover the masses and sky locations of the binary. We
present the results of this method applied to the mock LISA data Challenge 1B
data set.Comment: 11 pages, 2 figures, for GWDAW-12 proceedings edition of CQ
Report on the first round of the Mock LISA Data Challenges
The Mock LISA Data Challenges (MLDCs) have the dual purpose of fostering the
development of LISA data analysis tools and capabilities, and demonstrating the
technical readiness already achieved by the gravitational-wave community in
distilling a rich science payoff from the LISA data output. The first round of
MLDCs has just been completed: nine data sets containing simulated
gravitational wave signals produced either by galactic binaries or massive
black hole binaries embedded in simulated LISA instrumental noise were released
in June 2006 with deadline for submission of results at the beginning of
December 2006. Ten groups have participated in this first round of challenges.
Here we describe the challenges, summarise the results, and provide a first
critical assessment of the entries.Comment: Proceedings report from GWDAW 11. Added author, added reference,
clarified some text, removed typos. Results unchanged; Removed author, minor
edits, reflects submitted versio
Searching for gravitational waves from Cassiopeia A with LIGO
We describe a search underway for periodic gravitational waves from the
central compact object in the supernova remnant Cassiopeia A. The object is the
youngest likely neutron star in the Galaxy. Its position is well known, but the
object does not pulse in any electromagnetic radiation band and thus presents a
challenge in searching the parameter space of frequency and frequency
derivatives. We estimate that a fully coherent search can, with a reasonable
amount of time on a computing cluster, achieve a sensitivity at which it is
theoretically possible (though not likely) to observe a signal even with the
initial LIGO noise spectrum. Cassiopeia A is only the second object after the
Crab pulsar for which this is true. The search method described here can also
obtain interesting results for similar objects with current LIGO sensitivity.Comment: 8 pages, 1 figure; accepted to Classical and Quantum Gravit
Searching for gravitational waves from known pulsars
We present upper limits on the amplitude of gravitational waves from 28
isolated pulsars using data from the second science run of LIGO. The results
are also expressed as a constraint on the pulsars' equatorial ellipticities. We
discuss a new way of presenting such ellipticity upper limits that takes
account of the uncertainties of the pulsar moment of inertia. We also extend
our previous method to search for known pulsars in binary systems, of which
there are about 80 in the sensitive frequency range of LIGO and GEO 600.Comment: Accepted by CQG for the proceeding of GWDAW9, 7 pages, 2 figure
First LIGO search for gravitational wave bursts from cosmic (super)strings
We report on a matched-filter search for gravitational wave bursts from
cosmic string cusps using LIGO data from the fourth science run (S4) which took
place in February and March 2005. No gravitational waves were detected in 14.9
days of data from times when all three LIGO detectors were operating. We
interpret the result in terms of a frequentist upper limit on the rate of
gravitational wave bursts and use the limits on the rate to constrain the
parameter space (string tension, reconnection probability, and loop sizes) of
cosmic string models.Comment: 11 pages, 3 figures. Replaced with version submitted to PR
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