Diagnostics of timing noise in middle aged pulsars

TL;DR

This study measures and compares the timing noise in 129 middle-aged pulsars, revealing their lower noise levels compared to younger pulsars and implications for gravitational wave detection.

Contribution

It provides a comprehensive analysis of timing noise metrics in middle-aged pulsars and highlights variability not solely explained by spin-down rate.

Findings

Middle-aged pulsars exhibit less timing noise than younger pulsars.

Timing noise correlates strongly with spin-down rate but shows significant variability.

Implications suggest lower-than-expected noise levels in millisecond pulsars for gravitational wave detection.

Abstract

Radio pulsars are often used as clocks in a wide variety of experiments. Imperfections in the clock, known as timing noise, have the potential to reduce the significance of, or even thwart e.g. the attempt to find a stochastic gravitational wave (GW) background. We measure the timing noise in a group of 129 mostly middle-aged pulsars (i.e. characterstic ages near 1~Myr) observed with the Parkes radio telescope on a monthly basis since 2014. We examine four different metrics for timing noise, but it remains unclear which, if any, provides the best determination. In spite of this, it is evident that these pulsars have significantly less timing noise than their younger counterparts, but significantly more than the (much older) millisecond pulsars (MSPs). As with previous authors, we find a strong correlation between timing noise and the pulsar spin-down rate, $\dot{\nu}$. However, for a given $\dot{\nu}$ there is a spread of about a factor 30 in the strength of the timing noise likely indicating that nuclear conditions in the interior of the stars differs between objects. We briefly comment on the implications for GW detection through pulsar timing arrays as the level of timing noise in MSPs may be less than predicted.