RXTE/HEXTE Analysis of the Crab Pulsar Glitch of July 2000

TL;DR

This paper presents a detailed timing analysis of the Crab pulsar glitch in July 2000 using RXTE/HEXTE hard X-ray data, revealing changes in rotation frequency, decay timescale, and pulse profile characteristics.

Contribution

It provides the first detailed phase coherent timing solution for the Crab pulsar glitch in hard X-rays, including a novel measurement of the decay timescale.

Findings

Measured step change in rotation frequency and its consistency with radio data

Estimated decay timescale of the glitch at approximately 4.7 days

Observed a possible decrease in photon flux after the glitch

Abstract

Hard xray data from the RXTE observatory (HEXTE energy range 15 to 240 keV) have been analyzed to obtain a phase coherent timing solution for the Crab pulsar glitch of 15 July 2000. The results are: (1) step change in the rotation frequency $\nu_0$ of the Crab pulsar at the epoch of the glitch is $\Delta \nu_0 = (30 \pm 3) \times 10^{-9} \times \nu_0$, (2) step change in its time derivative is $\Delta \dot \nu_0 = (4.8 \pm 0.6) \times 10^{-3} \times \dot \nu_0$, and (3) the time scale of decay of the the step change is $\tau_d = 4.7 \pm 0.5$ days. The first two results are consistent with those obtained at radio frequencies by the Jodrell Bank observatory. The last result has not been quoted in the literature, but could be an underestimate due to lack of observations very close to the glitch epoch. By comparing with the monthly timing ephemeris published by the Jodrell group for the Crab pulsar, the time delay between the main peaks of the hard xray and radio pulse profiles is estimated to be $+411 \pm 167$ $\mu$sec. Although this number is not very significant, it is consistent with the number derived for the 2 to 16 keV energy range, using the PCA instrument of RXTE. The separation between the two peaks of the integrated pulse profile of the Crab pulsar, and the ratio of their intensities, both are statistically similar before and after the glitch. The dead time corrected integrated photon flux within the integrated pulse profile appears to decrease after the glitch, although this is not a statistically strong result. This work achieves what can be considered to be almost absolute timing analysis of the Crab pulsar hard xray data.