Discovery of pulsations from the Be/X-ray binary RXJ0101.3-7211 in the SMC by XMM-Newton ^*

¹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, Postfach 1312, 85741 Garching, Germany
² Lawerence Livermore National Laboratory, 7000 East Av., Livermore, CA 94550-9234, USA

Corresponding author: M. Sasaki, manami@mpe.mpg.de

Received: 14 February 2001
Accepted: 21 February 2001

Abstract

We report pulsations in the X-ray flux of RX J0101.3-7211 in the Small Magellanic Cloud (SMC) with a period of () s in XMM-Newton EPIC-PN data. The X-ray spectrum can be described by a power-law with a photon index of . 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.