SIMBAD references

We present a comprehensive study of the periodic variations observed in OGLEI-band light curves of Small Magellanic Cloud (SMC) Be/X-ray binaries, discovering new optical periodicities in nine systems. We find that these periodicities are derived from a number of mechanisms, notably disturbance of the decretion disc on the orbital period of the system, and aliased non-radial pulsations. We develop metrics that allow these mechanisms to be distinguished on the basis of the shape of the folded optical light curve, and use these metrics to categorize the periodicities present in ∼50 SMC binary systems. We conclude that extreme care must be taken in the interpretation of the OGLE light curves since only around 30 per cent of the periodicities present can be unambiguously attributed to orbital periods.