Did the Crab Pulsar Undergo a Small Glitch in 2006 late March/early April?

TL;DR

This paper suggests that the Crab Pulsar likely experienced a small glitch in early 2006, predating the known larger glitch in August, highlighting challenges in distinguishing small glitches from timing noise.

Contribution

It provides evidence for a previously unreported small glitch in the Crab Pulsar using radio and X-ray data, emphasizing the difficulty in detecting small glitches.

Findings

Probable small glitch occurred in March-April 2006

Analysis distinguishes small glitches from timing noise

Implications for understanding pulsar glitch behavior

Abstract

On 2006 August 23 the Crab Pulsar underwent a glitch, that was reported by the Jodrell Bank and the Xinjiang radio observatories. Neither data are available to the public. However, the Jodrell group publishes monthly arrival times of the Crab Pulsar pulse (their actual observations are done daily), using which it is shown that about five months earlier, the Crab Pulsar most probably underwent a small glitch, which has not been reported before. Neither observatory discusses the detailed analysis of data from 2006 March to August; either they may not have detected this small glitch, or may have attributed it to timing noise in the Crab Pulsar. The above result is verified using X-ray data from the RXTE observatory. If this is indeed true, this may probably be the smallest glitch observed in the Crab Pulsar so far, whose implications are discussed. This work addresses the confusion possible between small magnitude glitches and timing noise in pulsars.