Pulse variation of the optical emission of Crab pulsar

TL;DR

This study analyzes the Crab pulsar's optical pulse stability using high-resolution observations, revealing short-term TOA variations, long-term shape changes, and detailed pulse structure insights.

Contribution

It provides new constraints on pulsar precession, detects pulse timing variations on hours scale, and examines long-term pulse shape evolution with high temporal resolution.

Findings

Limits on short-term free precession.

Detection of TOA variations over 1.5-2 hours.

Observation of long-term pulse shape changes.

Abstract

The stability of the optical pulse of the Crab pulsar is analyzed based on the 1 $\mu$s resolution observations with the Russian 6-meter and William Hershel telescopes equipped with different photon-counting detectors. The search for the variations of the pulse shape along with its arrival time stability is performed. Upper limits on the possible short time scale free precession of the pulsar are placed. The evidence of pulse time of arrival (TOA) variations on 1.5-2 hours time scale is presented, along with evidence of small light curve (shape and separation of main and secondary peaks) changes between data sets, on time scale of years. Also, the fine structure of the main pulse is studied.