EVOLUTION OF THE X-RAY PROFILE OF THE CRAB PULSAR

Using the archival data from the Rossi X-ray Timing Explorer, we study the evolution of the Crab pulsar's X-ray profile in a time span of 11 years. The X-ray profiles, as characterized by a few parameters, changed slightly, but with high statistical significance in these years: the separation of the two peaks increased with a rate of 088 ± 020 per century, the flux ratio of the second pulse to the first pulse decreased by per century, and the pulse widths of the two pulses represented by their full widths at half maxima decreased by and per century, respectively. The evolutionary trends of the X-ray profile are similar to that observed in radio, but with quantitative differences. Finally, we briefly discuss the constraints of these X-ray properties on the geometry of the emission region of this pulsar.

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