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

The International Pulsar Timing Array 2nd data release is the combination of data sets 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 per cent upper limits on their amplitude h(95). The most sensitive frequency is 10 nHz with h(95) = 9.1 x10(-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.

Automated summary

The International Pulsar Timing Array 2nd data release is a combination of worldwide collaboration data sets. The study focuses on searching for continuous waves: gravitational wave signals generated by individual supermassive black hole binaries in the local universe. No evidence of such signals was found, and 95% upper limits on their amplitude, h(95), were set. The most sensitive frequency was found to be 10 nHz with h(95) = 9.1 x10(-15), achieving the best upper limit to date at low and high frequencies in the PTA band due to improved observation cadence.