# An optimised gravitational wave follow-up strategy with the Australian Square Kilometre Array Pathfinder

## TL;DR

This paper proposes an optimized observing strategy for the ASKAP telescope to efficiently detect radio counterparts of neutron star mergers, improving follow-up success rates with limited telescope time.

## Contribution

It introduces a novel sky tiling approach tailored for ASKAP to enhance detection efficiency of electromagnetic counterparts to gravitational wave events.

## Key findings

- Optimized tiling strategy increases detection probability.
- Significant efficiency gains over naive coverage methods.
- Effective use of limited telescope time for transient follow-up.

## Abstract

The detection of a neutron star merger by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo gravitational wave detectors and the subsequent detection of an electromagnetic counterpart has opened a new era of transient astronomy. With upgrades to the Advanced LIGO and Advanced Virgo detectors and new detectors coming online in Japan and India, neutron star mergers will be detected at a higher rate in the future, starting with the O3 observing run which will begin in early 2019. The detection of electromagnetic emission from these mergers provides vital information about merger parameters and allows independent measurement of the Hubble constant. The Australian Square Kilometre Array Pathfinder (ASKAP) is expected to become fully operational early 2019 and its 30 deg$^2$ field of view will enable us to rapidly survey large areas of sky. In this work we explore prospects for detecting both prompt and long-term radio emission from neutron star mergers with ASKAP and determine an observing strategy that optimises the use of telescope time. We investigate different strategies to tile the sky with telescope pointings in order to detect radio counterparts with limited observing time, using 475 simulated gravitational wave events. Our results show a significant improvement in observing efficiency when compared with a na\"ive strategy of covering the entire localisation above some confidence threshold, even when achieving the same total probability covered.