180 research outputs found
Predictability of band-limited, high-frequency, and mixed processes in the presence of ideal low-pass filters
Pathwise predictability of continuous time processes is studied in
deterministic setting. We discuss uniform prediction in some weak sense with
respect to certain classes of inputs. More precisely, we study possibility of
approximation of convolution integrals over future time by integrals over past
time. We found that all band-limited processes are predictable in this sense,
as well as high-frequency processes with zero energy at low frequencies. It
follows that a process of mixed type still can be predicted if an ideal
low-pass filter exists for this process.Comment: 10 page
A coherent triggered search for single spin compact binary coalescences in gravitational wave data
In this paper we present a method for conducting a coherent search for single
spin compact binary coalescences in gravitational wave data and compare this
search to the existing coincidence method for single spin searches. We propose
a method to characterize the regions of the parameter space where the single
spin search, both coincident and coherent, will increase detection efficiency
over the existing non-precessing search. We also show example results of the
coherent search on a stretch of data from LIGO's fourth science run but note
that a set of signal based vetoes will be needed before this search can be run
to try to make detections.Comment: 14 pages, 4 figure
LISA Data Analysis using MCMC methods
The Laser Interferometer Space Antenna (LISA) is expected to simultaneously
detect many thousands of low frequency gravitational wave signals. This
presents a data analysis challenge that is very different to the one
encountered in ground based gravitational wave astronomy. LISA data analysis
requires the identification of individual signals from a data stream containing
an unknown number of overlapping signals. Because of the signal overlaps, a
global fit to all the signals has to be performed in order to avoid biasing the
solution. However, performing such a global fit requires the exploration of an
enormous parameter space with a dimension upwards of 50,000. Markov Chain Monte
Carlo (MCMC) methods offer a very promising solution to the LISA data analysis
problem. MCMC algorithms are able to efficiently explore large parameter
spaces, simultaneously providing parameter estimates, error analyses and even
model selection. Here we present the first application of MCMC methods to
simulated LISA data and demonstrate the great potential of the MCMC approach.
Our implementation uses a generalized F-statistic to evaluate the likelihoods,
and simulated annealing to speed convergence of the Markov chains. As a final
step we super-cool the chains to extract maximum likelihood estimates, and
estimates of the Bayes factors for competing models. We find that the MCMC
approach is able to correctly identify the number of signals present, extract
the source parameters, and return error estimates consistent with Fisher
information matrix predictions.Comment: 14 pages, 7 figure
Angular Resolution of the LISA Gravitational Wave Detector
We calculate the angular resolution of the planned LISA detector, a
space-based laser interferometer for measuring low-frequency gravitational
waves from galactic and extragalactic sources. LISA is not a pointed
instrument; it is an all-sky monitor with a quadrupolar beam pattern. LISA will
measure simultaneously both polarization components of incoming gravitational
waves, so the data will consist of two time series. All physical properties of
the source, including its position, must be extracted from these time series.
LISA's angular resolution is therefore not a fixed quantity, but rather depends
on the type of signal and on how much other information must be extracted.
Information about the source position will be encoded in the measured signal in
three ways: 1) through the relative amplitudes and phases of the two
polarization components, 2) through the periodic Doppler shift imposed on the
signal by the detector's motion around the Sun, and 3) through the further
modulation of the signal caused by the detector's time-varying orientation. We
derive the basic formulae required to calculate the LISA's angular resolution
for a given source. We then evaluate for
two sources of particular interest: monchromatic sources and mergers of
supermassive black holes. For these two types of sources, we calculate (in the
high signal-to-noise approximation) the full variance-covariance matrix, which
gives the accuracy to which all source parameters can be measured. Since our
results on LISA's angular resolution depend mainly on gross features of the
detector geometry, orbit, and noise curve, we expect these results to be fairly
insensitive to modest changes in detector design that may occur between now and
launch. We also expect that our calculations could be easily modified to apply
to a modified design.Comment: 15 pages, 5 figures, RevTex 3.0 fil
Methods for Reducing False Alarms in Searches for Compact Binary Coalescences in LIGO Data
The LIGO detectors are sensitive to a variety of noise transients of
non-astrophysical origin. Instrumental glitches and environmental disturbances
increase the false alarm rate in the searches for gravitational waves. Using
times already identified when the interferometers produced data of questionable
quality, or when the channels that monitor the interferometer indicated
non-stationarity, we have developed techniques to safely and effectively veto
false triggers from the compact binary coalescences (CBCs) search pipeline
Searching for Gravitational Waves from Binary Inspirals with LIGO
We describe the current status of the search for gravitational waves from
inspiralling compact binary systems in LIGO data. We review the result from the
first scientific run of LIGO (S1). We present the goals of the search of data
taken in the second scientific run (S2) and describe the differences between
the methods used in S1 and S2.Comment: 9 pages, 2 figures. Published in proceedings of the 8th Gravitational
Wave Data Analysis Workshop, Milwaukee, WI, USA, 17-20 December 200
A Three-Stage Search for Supermassive Black Hole Binaries in LISA Data
Gravitational waves from the inspiral and coalescence of supermassive
black-hole (SMBH) binaries with masses ~10^6 Msun are likely to be among the
strongest sources for the Laser Interferometer Space Antenna (LISA). We
describe a three-stage data-analysis pipeline designed to search for and
measure the parameters of SMBH binaries in LISA data. The first stage uses a
time-frequency track-search method to search for inspiral signals and provide a
coarse estimate of the black-hole masses m_1, m_2 and of the coalescence time
of the binary t_c. The second stage uses a sequence of matched-filter template
banks, seeded by the first stage, to improve the measurement accuracy of the
masses and coalescence time. Finally, a Markov Chain Monte Carlo search is used
to estimate all nine physical parameters of the binary. Using results from the
second stage substantially shortens the Markov Chain burn-in time and allows us
to determine the number of SMBH-binary signals in the data before starting
parameter estimation. We demonstrate our analysis pipeline using simulated data
from the first LISA Mock Data Challenge. We discuss our plan for improving this
pipeline and the challenges that will be faced in real LISA data analysis.Comment: 12 pages, 3 figures, submitted to Proceedings of GWDAW-11 (Berlin,
Dec. '06
Detectability of gravitational wave events by spherical resonant-mass antennas
We have calculated signal-to-noise ratios for eight spherical resonant-mass
antennas interacting with gravitational radiation from inspiralling and
coalescing binary neutron stars and from the dynamical and secular bar-mode
instability of a rapidly rotating star. We find that by using technology that
could be available in the next several years, spherical antennas can detect
neutron star inspiral and coalescence at a distance of 15 Mpc and the dynamical
bar-mode instability at a distance of 2 Mpc.Comment: 39 pages, 4 EPS Figures, some additional SNRs for secular
instabilities, some changes to LIGO SNRs, Appendix added on the asymptotic
expansion of energy sensitivity, corrected supernova rates. Results available
at http://www.physics.umd.edu/rgroups/gen_rel_exp/snr.html Submitted to Phys.
Rev.
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
Observing binary inspiral in gravitational radiation: One interferometer
We investigate the sensitivity of individual LIGO/VIRGO-like interferometers
and the precision with which they can determine the characteristics of an
inspiralling binary system. Since the two interferometers of the LIGO detector
share nearly the same orientation, their joint sensitivity is similar to that
of a single, more sensitive interferometer. We express our results for a single
interferometer of both initial and advanced LIGO design, and also for the LIGO
detector in the limit that its two interferometers share exactly the same
orientation. We approximate the evolution of a binary system as driven
exclusively by leading order quadrupole gravitational radiation. To assess the
sensitivity, we calculate the rate at which sources are expected to be
observed, the range to which they are observable, and the precision with which
characteristic quantities describing the observed binary system can be
determined. Assuming a conservative rate density for coalescing neutron star
binary systems we expect that the advanced LIGO detector will observe
approximately 69~yr with an amplitude SNR greater than 8. Of these,
approximately 7~yr will be from binaries at distances greater than
950~Mpc. We explore the sensitivity of these results to a tunable parameter in
the interferometer design (the recycling frequency). The optimum choice of the
parameter is dependent on the goal of the observations, e.g., maximizing the
rate of detections or maximizing the precision of measurement. We determine the
optimum parameter values for these two cases.Comment: 40 pages (plus 7 figures), LaTeX/REVTEX3.0, NU-GR-
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