Searching for continuous Gravitational Waves in the second data release of the International Pulsar Timing Array

TL;DR

This paper searches for continuous gravitational waves from supermassive black hole binaries using the IPTA second data release, setting new upper limits and emphasizing the importance of noise modeling.

Contribution

It introduces an improved analysis method that accounts for complex noise features, leading to the most sensitive upper limits to date in PTA data.

Findings

No evidence for continuous gravitational waves was found.

Set the most sensitive upper limit at 10 nHz with h_95 = 9.1×10^-15.

Effective noise modeling is crucial for accurate upper limits.

Abstract

The International Pulsar Timing Array 2nd data release is the combination of datasets from worldwide collaborations. In this study, we search for continuous waves: gravitational wave signals produced by individual supermassive black hole binaries in the local universe. We consider binaries on circular orbits and neglect the evolution of orbital frequency over the observational span. We find no evidence for such signals and set sky averaged 95% upper limits on their amplitude h 95 . The most sensitive frequency is 10nHz with h 95 = 9.1 10-15 . We achieved the best upper limit to date at low and high frequencies of the PTA band thanks to improved effective cadence of observations. In our analysis, we have taken into account the recently discovered common red noise process, which has an impact at low frequencies. We also find that the peculiar noise features present in some pulsars data must be taken into account to reduce the false alarm. We show that using custom noise models is essential in searching for continuous gravitational wave signals and setting the upper limit.