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Name:Andry Rajoelimanana


Institution:SAAO / UCT


Country:South Africa




Title:Long-term properties of Be/X-ray binaries in the SMC.




Abstract:More than 60 High Mass X-ray Binaries (HMXBs) have been detected in the SMC, although its mass is one hundred times smaller than that of the Milky Way. The majority of these HMXBs are Be/X-ray binaries (BeX systems) consisting of an X-ray pulsar orbiting a rapidly rotating Be star in a wide and (often highly) eccentric orbit. We have used the combined light curves from MACHO and OGLE projects to study their long-term temporal properties. All the BeX in our sample display long-term quasi-periodic variations on timescales of ~ 200-3000 d. These superorbital modulations are believed to be related to the formation and depletion of the circumstellar disc around the Be star. The MACHO color of these systems show a loop-like structure in the color-magnitude diagram. In addition, we have also detected many of their optical orbital periodicities, visible as a series of precisely regular outbursts. Furthermore, the amplitude of these periodic outbursts can vary through the long-term superorbital cycle. We will discuss mechanisms which can produce this effect, as well as examining an apparent correlation between these periodicities.








            

            
            

              

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