On the common-spectrum process in the search for nanohertz gravitational-wave background

Boris Goncharov, Ryan Shannon, Daniel Reardon, George Hobbs, Andrew Zic, and the PPTA

With the NANOGrav collaboration, we find evidence for a common-spectrum process in the second data release (DR2) of the Parkes Pulsar Timing Array (PPTA). The process is expected from the stochastic gravitational-wave background, but it lacks evidence for spatial correlations required to claim a detection. We find that the process can not be explained by systematic errors in the position of the Solar System barycentre and by pure monopolar and dipolar correlations. However, we propose that the evidence for a common process can be caused by the rejection of the null hypothesis rather than by the presence of the signal with the same spectrum in all individual-pulsar data sets. We demonstrate two simulations that mimick the common red process.

The article is being reviewed by the steering committee of the International Pulsar Timing Array, more updates will be posted soon.

Recent Work