Evolution of the X-ray Profile of the Crab Pulsar

TL;DR

This study analyzes 11 years of RXTE data to observe subtle but significant changes in the X-ray profile of the Crab pulsar, revealing evolutionary trends similar to radio observations and providing insights into the pulsar's emission geometry.

Contribution

It presents the first long-term analysis of the Crab pulsar's X-ray profile evolution, quantifying parameter changes over a decade and comparing them with radio data.

Findings

Peak separation increased at 0.88±0.20 per century.

Flux ratio of second to first pulse decreased at (3.64±0.86)×10^{-2} per century.

Pulse widths of both pulses decreased over time.

Abstract

Using the archive data from the Rossi X-ray Timing Explorer ({\sl RXTE}), we have studied the evolution of the X-ray profile of the Crab pulsar in a time span of 11 years. The X-ray profiles, as characterized by a few parameters, changed slightly but significantly in these years: the separation of the two peaks increased with a rate $0.88\pm0.20\,\textordmasculine$\,per century, the flux ratio of the second pulse to the first pulse decreased with $(3.64\pm0.86)\times10^{-2}$\,per century, and the pulse widths of the two pulses descended with $1.44\pm0.15\,\textordmasculine$\, and $1.09\pm0.73\,\textordmasculine$\,per century, respectively. The evolutionary trends of the above parameters are similar to the radio results, but the values are different. We briefly discussed the constraints of these X-ray properties on the geometry of the emission region of this pulsar.