Long-term evolution of the neutron-star spin period of SXP 1062

TL;DR

This study investigates the long-term spin period evolution of the neutron star in SXP 1062, revealing a consistent spin-down trend and spectral features, providing insights into accretion physics in Be/X-ray binaries.

Contribution

It presents new XMM-Newton observations and multi-epoch data analysis, offering detailed measurements of spin period, spectral features, and disc evolution in SXP 1062, advancing understanding of neutron star spin dynamics.

Findings

Neutron star spin period measured at 1071.01 s in 2012.

SXP 1062 exhibits a net spin-down of 2.27 s/yr over 915 days.

Spectral analysis shows no cyclotron features, but emission lines suggest complex plasma conditions.

Abstract

The Be/X-ray binary SXP1062 is of especial interest owing to the large spin period of the neutron star, its large spin-down rate, and the association with a supernova remnant constraining its age. This makes the source an important probe for accretion physics. To investigate the long-term evolution of the spin period and associated spectral variations, we performed an XMM-Newton target-of-opportunity observation of SXP1062 during X-ray outburst. Spectral and timing analysis of the XMM-Newton data was compared with previous studies, as well as complementary Swift/XRT monitoring and optical spectroscopy with the SALT telescope were obtained. The spin period was measured to be P_s =(1071.01+-0.16) s on 2012 Oct 14. The X-ray spectrum is similar to that of previous observations. No convincing cyclotron absorption features, which could be indicative for a high magnetic field strength, are found. The high-resolution RGS spectra indicate the presence of emission lines, which may not completely be accounted for by the SNR emission. The comparison of multi-epoch optical spectra suggest an increasing size or density of the decretion disc around the Be star. SXP1062 showed a net spin-down with an average of (2.27+-0.44) s/yr over a baseline of 915 days.