4,427 research outputs found

### 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

### Gravitational Radiation

Gravity is one of the fundamental forces of Nature, and it is the dominant force in most astronomical systems. In common with all other phenomena, gravity must obey the principles of special relativity. In particular, gravitational forces must not be transmitted or communicated faster than light. This means that when the gravitational field of an object changes, the changes ripple outwards through space and take a finite time to reach other objects. These ripples are called gravitational radiation or gravitational waves. This article gives a brief introduction to the physics of gravitational radiation, including technical material suitable for non-specialist scientists

### Detection of gravitational waves from inspiraling compact binaries using a network of interferometric detectors

We formulate the data analysis problem for the detection of the Newtonian
waveform from an inspiraling compact-binary by a network of arbitrarily
oriented and arbitrarily distributed laser interferometric gravitational wave
detectors. We obtain for the first time the relation between the optimal
statistic and the magnitude of the network correlation vector, which is
constructed from the matched network-filter. This generalizes the calculation
reported in an earlier work (gr-qc/9906064), where the detectors are taken to
be coincident.Comment: 6 pages, RevTeX. Based on talk given at GWDAW-99, Rom

### Exact and Quasi-exact Models of Strange Stars

We construct and compare a variety of simple models for strange stars,
namely, hypothetical self-bound objects made of a cold stable version of the
quark-gluon plasma. Exact, quasi-exact and numerical models are examined to
find the most economical description for these objects. A simple and successful
parametrization of them is given in terms of the central density, and many
differences among the models are explicitly shown and discussed.Comment: 20 pp. 15 figures, to appear in IJMP

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