Broad-band spectral analysis of LMXB 2S 0921-63 with Suzaku

TL;DR

This study presents the first broad-band spectral analysis of the low-mass X-ray binary 2S 0921-63 up to 25 keV using Suzaku data, revealing spectral components and eclipse features.

Contribution

It provides the first comprehensive broad-band spectral analysis of 2S 0921-63, modeling its emission with thermal and Comptonization components.

Findings

Detection of a hot blackbody component with kT ~1.66-2.13 keV

Identification of a high-energy cutoff power law and Fe emission line

Observation of partial X-ray eclipse and intensity dip

Abstract

We present the broad-band spectral analysis of the low-mass X-ray binary 2S 0921-63 by using the Suzaku archival data covering the orbital phase between 0.31 and 1.16 during four close observations. It is the first time that a broad-band spectral analysis of 2S 0921-63 has been done up to 25 keV. The 0.5-10 keV XIS count rate varied between $\sim$ 1 and $\sim$ 5 counts s$^{-1}$ during the observations. A partial X-ray eclipse and broad post-eclipse intensity dip were observed during the observations. The X-ray emission hardened marginally during the intensity dip. We have modelled the source spectra by simultaneously fitting the XIS and HXD-PIN spectra for each of the four observations. The broad-band spectra of the source can be described by a model comprising a very hot blackbody having temperature, $kT_{\rm BB} \approx$ 1.66 - 2.13 keV, a high-energy cutoff power law, and an Fe emission line at $E_{\rm line} \sim$ 6.7 keV. A second model, accounting for the Comptonization of the thermal emission from accretion disc along with an Fe emission line, describes the broad-band spectra of 2S 0921-63 equally well.