Optimization of NANOGrav's Time Allocation for Maximum Sensitivity to Single Sources

TL;DR

This paper develops an optimized time allocation strategy for NANOGrav's pulsar array to enhance sensitivity to single gravitational wave sources, considering pulsar noise and source direction, leading to significant sensitivity improvements.

Contribution

It introduces a new method for optimizing pulsar time allocation in PTAs, accounting for intrinsic spin noise and source directionality, to maximize GW detection sensitivity.

Findings

Maximizing time on best-timed pulsars improves sensitivity.

Sensitivity gains range from 1.5 to 4 times.

Optimization varies with source position and pulsar noise characteristics.

Abstract

Pulsar Timing Arrays (PTAs) are a collection of precisely timed millisecond pulsars (MSPs) that can search for gravitational waves (GWs) in the nanohertz frequency range by observing characteristic signatures in the timing residuals. The sensitivity of a PTA depends on the direction of the propagating gravitational wave source, the timing accuracy of the pulsars, and the allocation of the available observing time. The goal of this paper is to determine the optimal time allocation strategy among the MSPs in the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) for a single source of GW under a particular set of assumptions. We consider both an isotropic distribution of sources across the sky and a specific source in the Virgo cluster. This work improves on previous efforts by modeling the effect of intrinsic spin noise for each pulsar. We find that, in general, the array is optimized by maximizing time spent on the best-timed pulsars, with sensitivity improvements typically ranging from a factor of 1.5 to 4.