2011A&A...527A.131S

One of the goals of the XMM-Newton survey of the Small Magellanic Cloud is to study the Be/X-ray binary population. During one of our first survey observations, a bright new transient - XMMUJ004814.0-732204 - was discovered. We present the analysis of the EPIC X-ray data, together with optical observations, to investigate the spectral and temporal characteristics of XMMUJ004814.0-732204 . We found coherent X-ray pulsations in the EPIC data with a period of (11.86642±0.00017)s. The X-ray spectrum can be modelled by an absorbed power law with an indication for a soft excess. Depending on the modelling of the soft X-ray spectrum, the photon index ranges between 0.53 and 0.66. We identify the optical counterpart as a B=14.9mag star that was monitored during the MACHO and OGLE-III projects. The optical light curves show regular outbursts by ∼0.5 mag in B and R and up to 0.9 mag in I, which repeat on a time scale of about 1000 days. The OGLE-III optical colours of the star are consistent with an early B spectral type. An optical spectrum obtained at the 1.9m telescope of the South African Astronomical Observatory in December 2009 shows Hαemission with an equivalent width of 3.5±0.6Å. The X-ray spectrum and the detection of pulsations suggest that XMMUJ004814.0-732204 is a new high-mass X-ray binary pulsar in the SMC. The long term variability and the Hαemission line in the spectrum of the optical counterpart identify it as a Be/X-ray binary system.