Multimessenger astrophysics drives the case for an Australian Gravitational-Wave observatory

Abstract

The next generation of an international network of gravitational-wave observatories is now in the advanced planning stages. With Australia's substantial history of contributions in this field, its history of scientific mega-projects like the Square Kilometer Array, and its unique geographic location and conditions, it is ideally placed to host an observatory in the global network. It has already been demonstrated that a gravitational wave detector in Australia plays an important role in minimizing the sky localization uncertainty of gravitational wave events. We study a particular science case for an Australian observatory, focusing on its potential contributions to multimessenger astronomy. We demonstrate that an observatory in Australia can enable the detection of up to eight multimessenger gravitational-wave plus kilonova events per year, with localisations better than $1-10°^2$ in both second- and third-generation networks. We show that, in a global network of XG observatories, an Australian observatory with 2G sensitivity would still enable significant advances in multimessenger science. The full case for an Australian observatory must be considered in a much broader context; however, this work indicates it could make substantial contributions to multimessenger astrophysics.