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

Abstract

We 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 ◊ 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 ◊ 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 +0.08 -0.09 to 1.97 +0.05 -0.07) and temporal brightening [unabsorbed flux F unabs = (4.3 +/- 0.2) ◊ 10 -12 to 2.7 +0.1 -0.2 ◊ 10 -11 ergs cm -2 s -1 ] of the pulsar by ~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) ◊ 10 34 to 1.16 +0.03 -0.07 ◊ 10 35 ergs s -1, and the X-ray efficiency increased from 0.2% +/- 0.01% to 1.4 +0.04 -0.08 %. The observed X-ray brightening and softening of the pulsar suggests for the first time that this HBP is revealing itself as a magnetar.