Multiwaveband studies of the hard ROSAT SMC transient 1WGA J0053.8-7226:: a new X-ray pulsar

We report on two optical candidates for the counterpart to an X-ray source in the Small Magellanic Cloud, 1WGA J0053.8-7226, identified as a serendipitous X-ray source from the ROSAT Position Sensitive Proportional Counter (PSPC) archive, and also observed by the Einstein Imaging Proportional Counter. Its X-ray properties, namely the hard X-ray spectrum, flux variability and column density, indicate a hard, transient source, with a luminosity of similar to3.8 x 10(35) erg s(-1). XTE and ASCA observations have confirmed the source to be an X-ray pulsar, with a 46-s spin period. Our optical observations reveal two possible candidates within the error circle. Both exhibit strong H alpha and weaker H beta emission. The optical colours indicate that both objects are Be-type stars. The Be nature of the stars implies that the counterpart is most likely a Be/X-ray binary system. Subsequent infrared (IR) photometry (JHK) of one of the objects shows that the source varies by at least 0.5 mag, while the (J - K) measured nearly simultaneously with the UBVRI and spectroscopic observations indicate an IR excess of similar to0.3 mag.