Variability of the high magnetic field X-ray pulsar psr j1846-0258 associated with the supernova remnant KES 75 as revealed by the Chandra X-ray observatory

present results from the archival Chandra observations of the 0.3 s X-ray pulsar PSR J1846-0258 associated with the supernova remnant ( SNR) Kes 75. The pulsar has the highest spin-down luminosity (E = 8.3 x 10(36) ergs s(-1)) among all the high magnetic field pulsars (HBPs) and has been classified as a Crab-like pulsar despite its magnetic field ( 5 x 10(13) G) being above the quantum critical field. It is the only HBP described by a nonthermal Crab-like spectrum, powering a bright pulsar wind nebula (PWN). Our spectroscopic study shows evidence of spectral softening (photon index Gamma = 1.32(-0.09)(+0.08) to 1.97(-0.07)(+0.05)) and temporal brightening [unabsorbed flux F-unabs = (4.3 +/- 0.2) x 10(-12) to 2.7-0.2+0.1 x 10(-11) ergs cm(-2) s(-1)] of the pulsar by similar to 6 times from 2000 to 2006. The 0.5-10 keV luminosity of the pulsar at the revised distance of 6 kpc has also increased from L-X = (1.85 +/- 0.08) x 10(34) to 1.16(-0.07)(+0.03) x 10(35) ergs s(-1), and the X-ray efficiency increased from 0.2% +/- 0.01% to 1.4(-0.08)(+0.04)%. The observed X-ray brightening and softening of the pulsar suggests for the first time that this HBP is revealing itself as a magnetar.