NuSTAR Observations of Magnetar 1E 1841–045

Abstract

We report new spectral and temporal observations of the magnetar 1E 1841–045 in the Kes 73 supernova remnant obtained with the Nuclear Spectroscopic Telescope Array. Combined with new Swift and archival XMM-Newton and Chandra observations, the phase-averaged spectrum is well characterized by a blackbody plus double power law, in agreement with previous multimission X-ray results. However, we are unable to reproduce the spectral results reported based on Suzaku observations. The pulsed fraction of the source is found to increase with photon energy. The measured rms pulsed fractions are ~12% and ~17% at ~20 and ~50 keV, respectively. We detect a new feature in the 24-35 keV band pulse profile that is uniquely double peaked. This feature may be associated with a possible absorption or emission feature in the phase-resolved spectrum. We fit the X-ray data using the recently developed electron-positron outflow model by Beloborodov for the hard X-ray emission from magnetars. This produces a satisfactory fit, allowing a constraint on the angle between the rotation and magnetic axes of the neutron star of ~20° and on the angle between the rotation axis and line of sight of ~50°. In this model, the soft X-ray component is inconsistent with a single blackbody; adding a second blackbody or a power-law component fits the data. The two-blackbody interpretation suggests a hot spot of temperature kT ≈ 0.9 keV occupying ~1% of the stellar surface.