Variability of the High Magnetic Field X-Ray Pulsar PSR J1846-0258 Associated with the Supernova Remnant Kes 75 as Revealed by the <i>Chandra X-Ray Observatory</i>

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 ( = 8.3 × 1036 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 × 1013 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 Γ = 1.32 + 0.08−0.09 to 1.97 + 0.05−0.07 ) and temporal brightening [unabsorbed flux Funabs = (4.3 ± 0.2) × 10−12 to 2.7−0.2+0.1 × 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 LX = (1.85 ± 0.08) × 1034 to 1.16 + 0.03−0.07 × 1035 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.