Timing of young radio pulsars I: Timing noise, periodic modulation and proper motion

TL;DR

This study develops a Bayesian method to model timing noise in young pulsars, revealing its properties, scaling relations, and detecting proper motions and periodic modulations in pulsar timing data.

Contribution

It introduces an improved Bayesian approach for simultaneous modeling of stochastic and deterministic pulsar timing parameters, advancing understanding of timing noise and pulsar kinematics.

Findings

Timing noise scales with pulsar spin frequency and spin-down rate.

Significant braking indices measured for 19 pulsars.

Proper motions detected for two pulsars and periodic modulations in five.

Abstract

The smooth spin-down of young pulsars is perturbed by two non-deterministic phenomenon, glitches and timing noise. Although the timing noise provides insights into nuclear and plasma physics at extreme densities, it acts as a barrier to high-precision pulsar timing experiments. An improved methodology based on Bayesian inference is developed to simultaneously model the stochastic and deterministic parameters for a sample of 85 high-$\dot{E}$ radio pulsars observed for $\sim$ 10 years with the 64-m Parkes radio telescope. Timing noise is known to be a red process and we develop a parametrization based on the red-noise amplitude ($A_{\rm red}$) and spectral index ($\beta$). We measure the median $A_{\rm red}$ to be $-10.4^{+1.8}_{-1.7}$ yr$^{3/2}$ and $\beta$ to be $-5.2^{+3.0}_{-3.8}$ and show that the strength of timing noise scales proportionally to $\nu^{1}|\dot{\nu}|^{-0.6\pm0.1}$, where $\nu$ is the spin frequency of the pulsar and $\dot{\nu}$ its spin-down rate. Finally, we measure significant braking indices for 19 pulsars, proper motions for two pulsars and discuss the presence of periodic modulation in the arrival times of five pulsars.