Optimal strategies for continuous wave detection in pulsar timing arrays: Realistic pulsar noise and a gravitational wave background

TL;DR

This paper evaluates the effectiveness of the Fp-statistic in detecting continuous gravitational waves in pulsar timing arrays, considering realistic pulsar noise and gravitational wave backgrounds, and confirms no detection in recent data.

Contribution

It analyzes the impact of pulsar red noise and GWB on the Fp-statistic, comparing marginalization and maximum-likelihood approaches, and applies the method to real data.

Findings

Little difference between marginalizing over and fixing red noise.

No evidence for continuous waves in the NANOGrav 12.5-year data.

Results align with previous Bayesian analyses.

Abstract

Pulsar timing arrays are sensitive to low-frequency gravitational waves (GWs), such as those produced by supermassive binary black holes at subparsec separations. The incoherent superposition of GWs emitted by a cosmological population of these sources produces a gravitational wave background (GWB), while some individual sources may be resolvable as deterministic signals with slowly varying GW frequencies, which are often referred to as "continuous waves" (CWs). The Fp-statistic is a frequentist method of detecting these CWs. In this paper, we study how the presence of pulsar red noise and a GWB affect the Fp-statistic. We compare results when marginalizing over the red noise and using the maximum-likelihood values of the red noise, and find little difference between the two. We also present results of using the Fp-statistic to analyze the NANOGrav 12.5-year data set, where we find no evidence for CWs in agreement with the previously published Bayesian results.