Spectral analysis of SMC X-2 during its 2015 outburst

Abstract

We report on the results of XMM-Newton and Swift observations of SMC X-2 during its last outburst in 2015 October, the first one since 2000. The source reached a very high luminosity (L ∼ 10<SUP>38</SUP> erg s<SUP>-1</SUP>), which allowed us to perform a detailed analysis of its timing and spectral properties. We obtained a pulse period P<SUB>spin</SUB> = 2.372267(5) s and a characterization of the pulse profile also at low energies. The main spectral component is a hard (Γ ≃ 0) power-law model with an exponential cut-off, but at low energies we detected also a soft (with kT ≃ 0.15 keV) thermal component. Several emission lines are present in the spectrum. Their identification with the transition lines of highly ionized N, O, Ne, Si, and Fe suggests the presence of photoionized matter around the accreting source.