Discovery of pulsations from the Be/X-ray binary RX J0101.3-7211 in the SMC by XMM-Newton

Abstract

We report pulsations in the X-ray flux of RX J0101.3-7211 in the Small Magellanic Cloud (SMC) with a period of (455 ± 2) s in XMM-Newton EPIC-PN data. The X-ray spectrum can be described by a power-law with a photon index of 0.6 ± 0.1. Timing analysis of ROSAT PSPC and HRI archival data confirms the pulsations and indicates a period increase of ∼5 s since 1993. RX J0101.3-7211 varied in brightness during the ROSAT observations with timescales of years with a maximum unabsorbed flux of 6 10-13 erg cm-2 s-1 (0.1-2.4 keV). The flux during the XMM-Newton observation in the ROSAT band was lower than during the faintest ROSAT detection. The unabsorbed luminosity derived from the EPIC-PN spectrum is 2 1035 erg s-1 (0.2-10.0 keV) assuming a distance of 60 kpc. Optical spectra of the proposed counterpart taken at the 2.3 m telescope of MSSSO in Australia in August 2000 show strong Hα emission and indicate a Be star. The X-ray and optical data confirm RX J0101.3-7211 as a Be/X-ray binary pulsar in the SMC.