97 research outputs found
Stochastic Background Search Correlating ALLEGRO with LIGO Engineering Data
We describe the role of correlation measurements between the LIGO
interferometer in Livingston, LA, and the ALLEGRO resonant bar detector in
Baton Rouge, LA, in searches for a stochastic background of gravitational
waves. Such measurements provide a valuable complement to correlations between
interferometers at the two LIGO sites, since they are sensitive in a different,
higher, frequency band. Additionally, the variable orientation of the ALLEGRO
detector provides a means to distinguish gravitational wave correlations from
correlated environmental noise. We describe the analysis underway to set a
limit on the strength of a stochastic background at frequencies near 900 Hz
using ALLEGRO data and data from LIGO's E7 Engineering Run.Comment: 8 pages, 2 encapsulated PostScript figures, uses IOP class files,
submitted to the proceedings of the 7th Gravitational Wave Data Analysis
Workshop (which will be published in Classical and Quantum Gravity
An Effective Search Method for Gravitational Ringing of Black Holes
We develop a search method for gravitational ringing of black holes. The
gravitational ringing is due to complex frequency modes called the quasi-normal
modes that are excited when a black hole geometry is perturbed. The detection
of it will be a direct confirmation of the existence of a black hole. Assuming
that the ringdown waves are dominated by the fundamental mode with least
imaginary part, we consider matched filtering and develop an optimal method to
search for the ringdown waves that have damped sinusoidal wave forms.
When we use the matched filtering method, the data analysis with a lot of
templates required. Here we have to ensure a proper match between the filter as
a template and the real wave. It is necessary to keep the detection efficiency
as high as possible under limited computational costs.
First, we consider the white noise case for which the matched filtering can
be studied analytically. We construct an efficient method for tiling the
template space. Then, using a fitting curve of the TAMA300 DT6 noise spectrum,
we numerically consider the case of colored noise. We find our tiling method
developed for the white noise case is still valid even if the noise is colored.Comment: 17 pages, 9 figures. Accepted to Phys. Rev. D, Note correction to Eq.
(3-25), A few comments added and minor typos correcte
The Allegro gravitational wave detector: Data acquisition and analysis
We discuss the data acquisition and analysis procedures used on the Allegro
gravity wave detector, including a full description of the filtering used for
bursts of gravity waves. The uncertainties introduced into timing and signal
strength estimates due to stationary noise are measured, giving the windows for
both quantities in coincidence searches.Comment: 26 pages, 18 figure
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
Study of the coincidences between the gravitational wave detectors EXPLORER and NAUTILUS in 2001
We report the result from a search for bursts of gravitational waves using
data collected by the cryogenic resonant detectors EXPLORER and NAUTILUS during
the year 2001, for a total measuring time of 90 days. With these data we
repeated the coincidence search performed on the 1998 data (which showed a
small coincidence excess) applying data analysis algorithms based on known
physical characteristics of the detectors. With the 2001 data a new interesting
coincidence excess is found when the detectors are favorably oriented with
respect to the Galactic Disk
The TIGA technique for detecting gravitational waves with a spherical antenna
We report the results of a theoretical and experimental study of a spherical
gravitational wave antenna. We show that it is possible to understand the data
from a spherical antenna with 6 radial resonant transducers attached to the
surface in the truncated icosahedral arrangement. We find that the errors
associated with small deviations from the ideal case are small compared to
other sources of error, such as a finite signal-to-noise ratio. An in situ
measurement technique is developed along with a general algorithm that
describes a procedure for determining the direction of an external force acting
on the antenna, including the force from a gravitational wave, using a
combination of the transducer responses. The practicality of these techniques
was verified on a room-temperature prototype antenna.Comment: 15 pages, 14 figures, submitted to Physical Review
Initial operation of the International Gravitational Event Collaboration
The International Gravitational Event Collaboration, IGEC, is a coordinated
effort by research groups operating gravitational wave detectors working
towards the detection of millisecond bursts of gravitational waves. Here we
report on the current IGEC resonant bar observatory, its data analysis
procedures, the main properties of the first exchanged data set. Even though
the available data set is not complete, in the years 1997 and 1998 up to four
detectors were operating simultaneously. Preliminary results are mentioned.Comment: 8 pages, 2 figures, 3 tables; Proceeding of the GWDAW'99. Submitted
to the International Journal of Modern Physic
All-sky search of NAUTILUS data
A search for periodic gravitational-wave signals from isolated neutron stars
in the NAUTILUS detector data is presented. We have analyzed half a year of
data over the frequency band Hz/s and over the entire sky. We have divided the
data into 2 day stretches and we have analyzed each stretch coherently using
matched filtering. We have imposed a low threshold for the optimal detection
statistic to obtain a set of candidates that are further examined for
coincidences among various data stretches. For some candidates we have also
investigated the change of the signal-to-noise ratio when we increase the
observation time from two to four days. Our analysis has not revealed any
gravitational-wave signals. Therefore we have imposed upper limits on the
dimensionless gravitational-wave amplitude over the parameter space that we
have searched. Depending on frequency, our upper limit ranges from to . We have attempted a statistical
verification of the hypotheses leading to our conclusions. We estimate that our
upper limit is accurate to within 18%.Comment: LaTeX, 12 page
Gravitational waves from coalescing binaries and Doppler experiments
Doppler tracking of interplanetary spacecraft provides the only method
presently available for broad-band searches of low frequency gravitational
waves. The instruments have a peak sensitivity around the reciprocal of the
round-trip light-time T of the radio link connecting the Earth to the
space-probe and therefore are particularly suitable to search for coalescing
binaries containing massive black holes in galactic nuclei. A number of Doppler
experiments -- the most recent involving the probes ULYSSES, GALILEO and MARS
OBSERVER -- have been carried out so far; moreover, in 2002-2004 the CASSINI
spacecraft will perform three 40 days data acquisition runs with expected
sensitivity about twenty times better than that achieved so far. Central aims
of this paper are: (i) to explore, as a function of the relevant instrumental
and astrophysical parameters, the Doppler output produced by in-spiral signals
-- sinusoids of increasing frequency and amplitude (the so-called chirp); (ii)
to identify the most important parameter regions where to concentrate intense
and dedicated data analysis; (iii) to analyze the all-sky and all-frequency
sensitivity of the CASSINI's experiments, with particular emphasis on possible
astrophysical targets, such as our Galactic Centre and the Virgo Cluster.Comment: 52 pages, LaTeX, 19 Postscript Figures, submitted to Phys. Rev.
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