Timing noise analysis of 27 HartRAO radio pulsars

Abstract

Timing observations on 27 radio pulsars obtained at Hartebeesthoek Radio Astronomy Observatory' (HanRAO) between 1984 and 1999 were analyzed in order to provide an in-depth empirical description of continuous, random rotational fluctuations in radio pulsars. The results of the detailed tinte-domain analyses, which are based on the strength parameter and structure function techniques, show that (i) the observed rotational fluctuations in five pulsars are apparently too weak to allow for any nteaningful timing noise analysis; (ii) the timing activity of most (> 60%) of the remainder of 22 pulsars cannot be explained in terms ofsimple idealized randont walk processes only and (iii) the observed timing activity of three, three, and two objects are characterised by rotational fluctuations whose statistics appear consistent with random walks in pulse phase, pulse frequency and slowing down rate, respectively. We discuss the results in the framework of the current understanding of radio pulsar timing noise phenomenology.