Optimizing Pulsar Timing Arrays to Maximize Gravitational Wave Single Source Detection: a First Cut

TL;DR

This paper presents a method to optimize Pulsar Timing Arrays for detecting single gravitational wave sources by analyzing sensitivity as a function of pulsar placement and observation time, offering strategies to improve detection volume.

Contribution

It introduces a simple calculation method for PTA sensitivity based on pulsar data and suggests optimal pulsar search and observation strategies for enhanced gravitational wave detection.

Findings

Prioritizing low-noise pulsars enhances sensitivity.

Adding pulsars near existing sensitive regions improves detection volume.

Focusing observation time on already sensitive pulsars yields better results.

Abstract

Pulsar Timing Arrays (PTAs) use high accuracy timing of a collection of low timing noise pulsars to search for gravitational waves in the microhertz to nanohertz frequency band. The sensitivity of such a PTA depends on (a) the direction of the gravitational wave source, (b) the timing accuracy of the pulsars in the array and (c) how the available observing time is allocated among those pulsars. Here, we present a simple way to calculate the sensitivity of the PTA as a function of direction of a single GW source, based only on the location and root-mean-square residual of the pulsars in the array. We use this calculation to suggest future strategies for the current North American Nanohertz Observatory for Gravitational Waves (NANOGrav) PTA in its goal of detecting single GW sources. We also investigate the affects of an additional pulsar on the array sensitivity, with the goal of suggesting where PTA pulsar searches might be best directed. We demonstrate that, in the case of single GW sources, if we are interested in maximizing the volume of space to which PTAs are sensitive, there exists a slight advantage to finding a new pulsar near where the array is already most sensitive. Further, the study suggests that more observing time should be dedicated to the already low noise pulsars in order to have the greatest positive effect on the PTA sensitivity. We have made a web-based sensitivity mapping tool available at http://gwastro.psu.edu/ptasm.