A possible precursor for the detection of nanohertz gravitational waves or unmodeled pulsar noise?
Boris Goncharov, Daniel Reardon, Ryan Shannon, Xing-Jiang Zhu, Eric Thrane and the PPTA
Pulsar timing arrays monitor pulse arrival times from millisecond radio pulsars with the main goal to detect the stochastic nanohertz gravitational-wave background from supermassive black hole binaries. As data sets get larger and radio-telescopes become more sensitive, new sources of noise appear. We find and characterize these new sources of noise with the second data release (DR2) of the Parkes Pulsar Timing Array (PPTA). Our models will help gravitational-wave searches and open new pathways to study pulsars and the interstellar medium. We find:
- New stochastic chromatic noise processes, which depend on the radio-frequency;
- Radio-frequency-dependent exponential dips to be corresponding to sudden changes in pulse profiles;
- New sources of band- and system-dependent red noise;
- The way to evaluate global performance of noise models, which complements Bayesian model selection;
- That achromatic red noise, on average has a steeper spectrum than band noise and system noise;
- Our best noise models for a few pulsars are still not sufficient to describe pulse arrival times.
We model red noise and link exponential dips in residuals with pulse shape changes