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

Gravitational Wave Astronomy: Delivering on the Promises

Now that LIGO and Virgo have begun to detect gravitational wave events with regularity, the field of gravitational wave astronomy is beginning to realise its promise. Binary black holes and, very recently, binary neutron stars have been observed, and we are already learning much from them. The future, with improved sensitivity, more detectors, and detectors like LISA in different frequency bands, has even more promise to open a completely hidden side of the Universe to our exploration.Comment: 12 pages, 1 figure, presented at a discussion meeting "Promises of gravitational wave astronomy" held at the Royal Society London, 11 September 201

Sources of gravitational waves

Sources of low frequency gravitational radiation are reviewed from an astrophysical point of view. Cosmological sources include the formation of massive black holes in galactic nuclei, the capture by such holes of neutron stars, the coalescence of orbiting pairs of giant black holes, and various means of producing a stochastic background of gravitational waves in the early universe. Sources local to our Galaxy include various kinds of close binaries and coalescing binaries. Gravitational wave astronomy can provide information that no other form of observing can supply; in particular, the positive identification of a cosmological background originating in the early universe would be an event as significant as was the detection of the cosmic microwave background

Sources of radiation from neutron stars

I give a brief introduction to the problem of detecting gravitational radiation from neutron stars. After a review of the mechanisms by which such stars may produce radiation, I consider the different search strategies appropriate to the different kinds of sources: isolated known pulsars, neutron stars in binaries, and unseen neutron stars. The problem of an all-sky survey for unseen stars is the most taxing one that we face in analysing data from interferometers. I describe the kinds of hierarchical methods that are now being investigated to reach the maximal sensitivity, and I suggest a replacement for standard Fourier-transform search methods that requires fewer floating-point operations for Fourier-based searches over large parameter spaces, and in addition is highly parallelizable, working just as well on a loosely coupled network of workstations as on a tightly coupled parallel computer.Comment: 11 pages, no figure

Getting Ready for GEO600 Data

Data of good quality is expected from a number of gravitational wave detectors within the next two years. One of these, GEO600, has special capabilities, such as narrow-band operation. I describe here the preparations that are currently being made for the analysis of GEO600 data.Comment: 17 pages, 7 figures, proceedings of Yukawa International Seminar 199

Binary neutron star inspiral, LIGO, and cosmology

Recent work on the expected event rate of neutron star inspiral signals in the LIGO detector is summarized. The observed signals will be from inspirals at cosmological distances, and the important cosmological effects on the event rate and spectrum are discussed. This paper is a contribution to the proceedings of the 17th Texas Symposium held in Munich, 12-17 December 1994.Comment: 4 pages, REVTeX3.x, no figure

Time-Symmetric ADI and Causal Reconnection: Stable Numerical Techniques for Hyperbolic Systems on Moving Grids

Moving grids are of interest in the numerical solution of hydrodynamical problems and in numerical relativity. We show that conventional integration methods for the simple wave equation in one and more than one dimension exhibit a number of instabilities on moving grids. We introduce two techniques, which we call causal reconnection and time-symmetric ADI, which together allow integration of the wave equation with absolute local stability in any number of dimensions on grids that may move very much faster than the wave speed and that can even accelerate. These methods allow very long time-steps, are fully second-order accurate, and offer the computational efficiency of operator-splitting.Comment: 45 pages, 19 figures. Published in 1994 but not previously available in the electronic archive

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