Long-term XMM-Newton view of magnetar CXOU J010043.1$-$721134: Comprehensive spectral and temporal results

TL;DR

This study analyzes eleven XMM-Newton observations of the magnetar CXOU J010043.1-721134 from 2000 to 2016, revealing its spin properties, spectral characteristics, and pulse profile features, consistent with previous findings.

Contribution

It provides a comprehensive spectral and temporal analysis of the magnetar using long-term XMM-Newton data, including the first detailed spectral fitting with a thermal Comptonization model.

Findings

Spin period of 8.0275 s and period derivative of 1.76e-11 s/s

Double-peaked pulse profile with consistent pulse fractions across energy bands

Best spectral fit achieved with a thermal Comptonization model

Abstract

We present an in-depth analysis and results of eleven XMM-Newton datasets, spanning 2000 to 2016, of the anomalous X-ray Pulsar CXOU J010043.1$-$721134 which has been classified as a magnetar. We find a spin-period of 8.0275(1) s as of December 2016 and calculate the period derivative to be $(1.76\pm 0.02) \times 10^{-11}$ s s$^{-1}$, which translate to a dipolar magnetic field strength of $3.8\times 10^{14}$ G and characteristic age of $\sim 7200$ yr for the magnetar. It has a double-peaked pulse profile, with one broad and one narrow peak, in both soft ($0.3-1.3$ keV) and hard ($1.3-8$ keV) energy bands. The pulse fractions in the two energy bands are found to be consistent with constant values. These results are in agreement with previously published results for this source. Although two-component models produce acceptable fits to its energy spectra, single component models are much simpler and are able to explain the similarity of the pulse profiles in the low and high energy bands. We attempt fitting with four different single-component models and find that the best fit to the spectra is obtained by fitting a thermal Comptonization model with the photon index $(\Gamma)$ between $2.0-2.7$ and the electron temperature $(kT_e)$ between $0.5-0.9$ keV, for a seed blackbody photon distribution of 0.2 keV. Finally, we conclude by discussing our results briefly.