6,183 research outputs found
Gravitational wave sources: An overview
With full-sensitivity operation of the first generation of gravitational wave detectors now just around the corner, and with the LISA space-based detector entering its final design stage, I review the wide variety of predicted sources from the perspective of what further theoretical work may be needed to assist in their detection. Some sources, such as binary black holes, require good theoretical models from which search templates for matched filtering of the data streams can be computed. Others, such as searches for un-modelled bursts, require clever robust search algorithms not tied to detailed waveform models. Still others, such as searches for continuous waves from pulsars, are compute-bound and need improved efficient computer algorithms. The sensitivity of initial ground-based detectors will depend in part on how good we are at searching the data. In the longer term, the amount of information we can extract from the LISA data stream will depend in part on how good we are at removing strong signals so that we can recover the weaker ones as well
Introduction to the Analysis of Low-Frequency Gravitational Wave Data
The space-based gravitational wave detector LISA will observe in the
low-frequency gravitational-wave band (0.1 mHz up to 1 Hz). LISA will search
for a variety of expected signals, and when it detects a signal it will have to
determine a number of parameters, such as the location of the source on the sky
and the signal's polarisation. This requires pattern-matching, called matched
filtering, which uses the best available theoretical predictions about the
characteristics of waveforms. All the estimates of the sensitivity of LISA to
various sources assume that the data analysis is done in the optimum way.
Because these techniques are unfamiliar to many young physicists, I use the
first part of this lecture to give a very basic introduction to time-series
data analysis, including matched filtering. The second part of the lecture
applies these techniques to LISA, showing how estimates of LISA's sensitivity
can be made, and briefly commenting on aspects of the signal-analysis problem
that are special to LISA.Comment: 20 page
Low-Frequency Sources of Gravitational Waves: A Tutorial
Gravitational wave detectors in space, particularly the LISA project, can
study a rich variety of astronomical systems whose gravitational radiation is
not detectable from the ground, because it is emitted in the low-frequency
gravitational wave band (0.1 mHz to 1 Hz) that is inaccessible to ground-based
detectors. Sources include binary systems in our Galaxy and massive black holes
in distant galaxies. The radiation from many of these sources will be so strong
that it will be possible to make remarkably detailed studies of the physics of
the systems. These studies will have importance both for astrophysics (most
notably in binary evolution theory and models for active galaxies) and for
fundamental physics. In particular, it should be possible to make decisive
measurements to confirm the existence of black holes and to test, with
accuracies better than 1%, general relativity's description of them. Other
observations can have fundamental implications for cosmology and for physical
theories of the unification of forces. In order to understand these
conclusions, one must know how to estimate the gravitational radiation produced
by different sources. In the first part of this lecture I review the dynamics
of gravitational wave sources, and I derive simple formulas for estimating wave
amplitudes and the reaction effects on sources of producing this radiation.
With these formulas one can estimate, usually to much better than an order of
magnitude, the physics of most of the interesting low-frequency sources. In the
second part of the lecture I use these estimates to discuss, in the context of
the expected sensitivity of LISA, what we can learn by from observations of
binary systems, massive black holes, and the early Universe itself.Comment: 12 pages, 2 figure
Loosely coherent searches for sets of well-modeled signals
We introduce a high-performance implementation of a loosely coherent
statistic sensitive to signals spanning a finite-dimensional manifold in
parameter space. Results from full scale simulations on Gaussian noise are
discussed, as well as implications for future searches for continuous
gravitational waves. We demonstrate an improvement of more than an order of
magnitude in analysis speed over previously available algorithms. As searches
for continuous gravitational waves are computationally limited, the large
speedup results in gain in sensitivity
Removing Line Interference from Gravitational Wave Interferometer Data
We describe a procedure to identify and remove a class of interference lines
from gravitational wave interferometer data. We illustrate the usefulness of
this technique applying it to prototype interferometer data and removing all
those lines corresponding to the external electricity main supply and related
features.Comment: Latex 6 pages, 5 figures. To appear in: "Gravitational Wave Detection
II". Edt. Rie Sasaki; Universal Academy Press, Inc, Tokyo, Japa
An efficient Matched Filtering Algorithm for the Detection of Continuous Gravitational Wave Signals
We describe an efficient method of matched filtering over long (greater than
1 day) time baselines starting from Fourier transforms of short durations
(roughly 30 minutes) of the data stream. This method plays a crucial role in
the search algorithm developed by Schutz and Papa for the detection of
continuous gravitational waves from pulsars. Also, we discuss the computational
cost--saving approximations used in this method, and the resultant performance
of the search algorithm.Comment: 4 pages, text only, accepted for publication in the proceedings of
the 3rd Amaldi conference on gravitational wave
Geophysical parameters from the analysis of laser ranging to starlette
Starlette Satellite Laser Ranging (SLR) data were used, along with several other satellite data sets, for the solution of a preliminary gravity field model for TOPEX, PTGF1. A further improvement in the earth gravity model was accomplished using data collected by 12 satellites to solve another preliminary gravity model for TOPEX, designated PTGF2. The solution for the Earth Rotation Parameter (ERP) was derived from the analysis of SLR data to Starlette during the MERIT Campaign. Starlette orbits in 1976 and 1983 were analyzed for the mapping of the tidal response of the earth. Publications and conference presentations pertinent to research are listed
Lighthouses of Gravitational Wave Astronomy
Gravitational wave detectors capable of making astronomical observations could begin to operate within the next year, and over the next 10 years they will extend their reach out to cosmological distances, culminating in the space mission LISA. A prime target of these observatories will be binary systems, especially those whose orbits shrink measurably during an observation period. These systems are standard candles, and they offer independent ways of measuring cosmological parameters. LISA in particular could identify the epoch at which star formation began and, working with telescopes making electromagnetic observations, measure the Hubble flow at redshifts out to 4 or more with unprecedented accuracy
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