X-ray spectroscopy of the accretion disk corona source 2S 0921-630 with Suzaku archival data

Abstract

2S 0921$-$630 is an eclipsing low-mass X-ray binary (LMXB) with an orbital period of $\sim$ 9 days. Past X-ray observations have revealed that 2S 0921$-$630 has an extended accretion disk corona (ADC), from which most of the X-rays from the system are emitted. We report the result of our Suzaku archival data analysis of 2S 0921$-$630. The average X-ray spectrum is reproduced with a blackbody emission ($k{T}_{\mathrm{bb}}\sim 0.3$ keV) Comptonized by optically-thick gas (``Compton cloud''; optical depth $\tau \sim 21$) with a temperature of $\sim 2$ keV, combined with thirteen emission lines. We find that most of the emission lines correspond to highly ionized atoms: O, Ne, Mg, Si, S, Ar, and Fe. A K$\alpha$ emission line and an absorption edge of semi-neutral iron (Fe I -- XVII) are also detected. The semi-neutral iron K$\alpha$ line is significantly broad with a width of $0.11\pm 0.02$ keV in sigma, which corresponds to the Doppler broadening by the Kepler motion at a radius of $\sim 10^9$ cm. We suggest that the observed semi-neutral iron line originates at the inner part of the accretion disk in the immediate outside of the Compton cloud, i.e., the Compton cloud may have a radius of $\sim 10^9$ cm.

14 pages, 6 figures. Accepted for PASJ on 16 Oct 2022

References in corpus (4)

• A catalogue of low-mass X-ray binaries in the Galaxy, LMC, and SMC (Fourth edition)
• Spectral and temporal properties of Compton scattering by mildly relativistic thermal electrons
• The viscosity parameter alpha and the properties of accretion disc outbursts in close binaries
• On the mass of the neutron star in V395 Car/2S 0921-630

Cited by in corpus (3)

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