2015MNRAS.449.3710S

We report on an X-ray observation of the Be X-ray binary pulsar RX J0059.2-7138, performed by XMM-Newton in 2014 March. The 19 ks long observation was carried out about three months after the discovery of the latest outburst from this Small Magellanic Cloud transient, when the source luminosity was LX ∼ 10³⁸ erg/s. A spin period of Pspin=2.762 383(5) s was derived, corresponding to an average spin-up of {dot}P_spin = -(1.27±0.01)×10^-12 s/s from the only previous period measurement, obtained more than 20 years earlier. The time-averaged continuum spectrum (0.2-12 keV) consisted of a hard power-law (photon index ∼ 0.44) with an exponential cut-off at a phase-dependent energy ( ∼ 20-50 keV) plus a significant soft excess below ∼ 0.5 keV. In addition, several features were observed in the spectrum: an emission line at 6.6 keV from highly ionized iron, a broad feature at 0.9-1 keV likely due to a blend of Fe L-shell lines, and narrow emission and absorption lines consistent with transitions in highly ionized oxygen, nitrogen and iron visible in the high-resolution RGS data (0.4-2.1 keV). Given the different ionization stages of the narrow-line components, indicative of photoionization from the luminous X-ray pulsar, we argue that the soft excess in RX J0059.2-7138 is produced by reprocessing of the pulsar emission in the inner regions of the accretion disc.