X-ray reprocessing in accreting pulsar GX 301-2 observed with Insight-HXMT

TL;DR

This study analyzes X-ray reprocessing features in GX 301-2 using Insight-HXMT data, revealing orbital-dependent absorption, ionization states, and accretion environment inhomogeneities through spectral line analysis.

Contribution

It provides detailed spectral analysis of GX 301-2, highlighting the variability of local absorption and accretion environment characteristics across its orbit.

Findings

Detection of prominent Fe and Ni emission lines and absorption edges.

Correlation between local absorption and iron line equivalent width.

Inhomogeneous and spherically distributed accretion material inferred.

Abstract

We investigate the absorption and emission features in observations of GX 301-2 detected with Insight-HXMT/LE in 2017-2019. At different orbital phases, we found prominent Fe Kalpha, Kbeta and Ni Kalpha lines, as well as Compton shoulders and Fe K-shell absorption edges. These features are due to the X-ray reprocessing caused by the interaction between the radiation from the source and surrounding accretion material. According to the ratio of iron lines Kalpha and Kbeta, we infer the accretion material is in a low ionisation state. We find an orbital-dependent local absorption column density, which has a large value and strong variability around the periastron. We explain its variability as a result of inhomogeneities of the accretion environment and/or instabilities of accretion processes. In addition, the variable local column density is correlated with the equivalent width of the iron Kalpha lines throughout the orbit, which suggests that the accretion material near the neutron star is spherically distributed.