Time Evolution of the X-Ray and γ-Ray Fluxes of the Crab Pulsar

We studied the evolution of the X-ray and γ-ray spectra of the Crab pulsar utilizing the 11-year observations from the Rossi X-ray Timing Explorer (RXTE) and 9-year observations from the Fermi Gamma-ray Space Telescope (FGST). By fitting the spectrum of each observation, we obtained the corresponding flux and then analyzed the long-term evolution of the X-ray (or γ-ray) luminosities as well as their correlations with the spin-down power of the pulsar. The X-ray flux in 5–60 keV obtained by the Proportional Counter Array of RXTE decreases with a rate of (−2.4 ± 0.4) × 10−14 erg cm−2 s−1 per day. The X-ray flux in 15–250 keV obtained by the High Energy X-ray Timing Experiment of RXTE and the γ-ray flux in 0.1–300 GeV by the Large Area Telescope onboard FGST show similar decreasing trends but are insignificant statistically. The 5–60 keV X-ray luminosity LX is correlated with the spin-down power Lsd by , which is similar to the statistical results for young pulsars.