Networks of gravitational wave detectors and three figures of merit

TL;DR

This paper presents a framework for evaluating gravitational wave detector networks, demonstrating that adding new sites significantly boosts detection rates and directional accuracy, with universal probability distributions for key detection parameters.

Contribution

It introduces a universal pdf for detected SNR and orbital inclination, and proposes figures of merit to compare network performance, highlighting the benefits of expanding existing gravitational wave detector networks.

Findings

Adding new sites increases detection rates by factors of 2 to 4.

Moving detectors to Australia improves direction-finding by over 4 times.

Expanded networks could detect 300-400 neutron star mergers annually.

Abstract

This paper develops a general framework for studying the effectiveness of networks of interferometric gravitational wave detectors and then uses it to show that enlarging the existing LIGO-VIRGO network with one or more planned or proposed detectors in Japan (LCGT), Australia, and India brings major benefits, including much larger detection rate increases than previously thought... I show that there is a universal probability distribution function (pdf) for detected SNR values, which implies that the most likely SNR value of the first detected event will be 1.26 times the search threshold. For binary systems, I also derive the universal pdf for detected values of the orbital inclination, taking into account the Malmquist bias; this implies that the number of gamma-ray bursts associated with detected binary coalescences should be 3.4 times larger than expected from just the beaming fraction of the gamma burst. Using network antenna patterns, I propose three figures of merit that characterize the relative performance of different networks... Adding {\em any} new site to the planned LIGO-VIRGO network can dramatically increase, by factors of 2 to 4, the detected event rate by allowing coherent data analysis to reduce the spurious instrumental coincident background. Moving one of the LIGO detectors to Australia additionally improves direction-finding by a factor of 4 or more. Adding LCGT to the original LIGO-VIRGO network not only improves direction-finding but will further increase the detection rate over the extra-site gain by factors of almost 2, partly by improving the network duty cycle... Enlarged advanced networks could look forward to detecting three to four hundred neutron star binary coalescences per year.