Chandra Observation of the Anomalous X-Ray Pulsar 1E 1841−045

Abstract

Abstract We present the results from a Chandra ACIS CC mode observation of an anomalous X-ray pulsar (AXP) 1E 1841$-$045. This was the first observation in which the pulsar spectrum over a wide energy range was spatially discriminated from the surrounding SNR, Kes 73. Like other AXPs, the phase-integrated spectrum was fitted well with a power-law plus blackbody model. The spectral parameters are $\Gamma = 2.0 \pm 0.3$, $kT_\mathrm{BB} = 0.44 \pm 0.02 \,\mathrm{keV}$, and $N_\mathrm{H} = 2.54^{+0.15}_{-0.13} \times 10^{22} \,\mathrm{cm}^{-2}$. This photon index is the flattest among AXPs, and resembles soft gamma-ray repeaters (SGRs) in a quiescent state. The pulse profile is double-peaked, and we found that the second peak has a significantly hard spectrum. The spectra of all phases are consistent with a power-law plus blackbody model with a constant temperature and photon index. When fitted with a two-blackbody model, we obtained a similarly good fit. These results can be interpreted by saying that there are two emission regions with different energy spectra.