SALT observations of the Be/X-ray binary A0538-66

Abstract

The Be X-ray transient, A0538-66, is the most extreme LMC/SMC member of this class, exhibiting optical (and sometimes X-ray) outbursts with a period of 16.6d. More remarkably, long-term (MACHO) optical photometry revealed a large amplitude (∼0.5mag) 421d activity cycle which appears to control the appearance of the recurrent orbital outbursts/flares, as they are only seen during the minimum of the 421d cycle. The nature of the physical link between these features is very poorly understood, but is likely related to properties of the Be star's equatorial disc. We will present our recent results on the long-term spectroscopic observations of this LMC BeX system using both broad-band (wide wavelength coverage) as well as high resolution optical spectra obtained from the Southern African Large Telescope (SALT). These observations enable us to probe both the evolution of the Be star envelope and the details of its interaction with the neutron star in its presumed highly eccentric (e ∼ 0.7) orbit. The high resolution spectra also allows us to derive its rotational velocity and spectral classification.