Targeted search for an individual SMBHB in NANOGrav 15-year and EPTA DR2 data sets

TL;DR

This study conducts targeted Bayesian searches for continuous gravitational waves from the SMBHB candidate 3C 66B in two major PTA data sets, finding no evidence but setting upper limits on the source's parameters.

Contribution

It presents the first targeted Bayesian analysis of specific SMBHB candidates in PTA data, incorporating Hellings-Downs correlation assessments for GWB characterization.

Findings

No detection of continuous GWs from 3C 66B in both data sets.

Placed upper limits on GW amplitude and source chirp mass.

Reconfirmed non-detection when considering Hellings-Downs correlations.

Abstract

While pulsar timing array (PTA) collaborations have reported evidence for a stochastic gravitational wave background (GWB), the detection of continuous gravitational waves (GWs) from a confirmed supermassive black hole binary (SMBHB) would provide strong support for the SMBHB origin of GWB. In this study, we analyze continuous GWs from the SMBHB candidate 3C 66B, modeling the GWB as a common uncorrelated red noise. Using Bayesian methods, we perform targeted searches across two PTA data sets: Nanohertz Observatory for Gravitational Waves 15 years data set and the European Pulsar Timing Array DR2 full data set. We find no evidence of such signal in both data sets and then place upper limits on the amplitude of the signal and the chirp mass of the source. Additionally, we evaluate the case of a GWB characterized by Hellings-Downs correlations using a likelihood reweighting method, which consistently reconfirms the conclusion of non-detection.