Suzaku Observation of AXP 1E 1841-045 in SNR Kes 73

TL;DR

This study uses Suzaku X-ray observations to analyze the spectrum of AXP 1E 1841-045 across 0.4 to 50 keV, testing spectral models and revealing consistent emission characteristics suggestive of fundamental magnetar properties.

Contribution

It demonstrates that the NPEX spectral model fits the wide energy range data better than traditional models, providing new insights into magnetar emission mechanisms.

Findings

NPEX model fits both phase-averaged and phase-resolved spectra well.

Spectral photon indices remain constant across phases.

Spectral variations are clearly observed with the NPEX model.

Abstract

Anomalous X-ray pulsars (AXPs) are thought to be magnetars, which are neutron stars with ultra strong magnetic field of $10^{14}$-- $10^{15}$ G. Their energy spectra below $\sim$10 keV are modeled well by two components consisting of a blackbody (BB) ($\sim$0.4 keV) and rather steep power-law (POW) function (photon index $\sim$2-4). Kuiper et al.(2004) discovered hard X-ray component above $\sim$10 keV from some AXPs. Here, we present the Suzaku observation of the AXP 1E 1841-045 at the center of supernova remnant Kes 73. By this observation, we could analyze the spectrum from 0.4 to 50 keV at the same time. Then, we could test whether the spectral model above was valid or not in this wide energy range. We found that there were residual in the spectral fits when fit by the model of BB + POW. Fits were improved by adding another BB or POW component. But the meaning of each component became ambiguous in the phase-resolved spectroscopy. Alternatively we found that NPEX model fit well for both phase-averaged spectrum and phase-resolved spectra. In this case, the photon indices were constant during all phase, and spectral variation seemed to be very clear. This fact suggests somewhat fundamental meaning for the emission from magnetars.