Targeted Search for Eccentric Supermassive Binary Black Holes in OJ 287 and nearby Galaxy Clusters with PPTA DR3

Abstract

We perform Bayesian targeted searches for continuous gravitational waves from eccentric supermassive binary black holes (SMBBHs) using the Parkes Pulsar Timing Array third data release (PPTA DR3). Six electromagnetically motivated sky directions are analyzed, including the blazar OJ 287 and five nearby galaxy clusters (Virgo, Fornax, Norma, Hercules, and Coma). No significant signals are found. For OJ 287, by explicitly incorporating orbital eccentricity (up to e0 = 0.8) to robustly capture signal power spread across multiple harmonics, we constrain the total binary mass to Mtot < 5.25 × 1010M⊙ (95% credible level). We also place upper limits on the chirp mass of potential SMBBHs residing in..