Short term variability in Be stars and binaries in the Magellanic Clouds.
Résumé
We observed a large sample of B \& Be stars in the Magellanic Clouds, respectively 176 and 344 stars, with the multi-object spectrograph GIRAFFE at ESO/VLT. We obtained spectra at different settings at various epochs. It allowed us to discover several spectroscopic binaries with short and intermediate periods. By cross-correlation in coordinates with the MACHO database, we found the light-curves for 350 stars in our samples. Among them, 19 (14 new) are photometric binaries (5 in the LMC, 14 in the SMC). Among these 19 photometric binaries 6 are also spectroscopic binaries (5 in the LMC, 1 in the SMC) and 2 others are Be stars (2 in the SMC). For all these binaries the orbital period was determined. Among our sample, 134 Be stars were observed by MACHO and, for these stars, we searched for short-term photometric variability. We have found 13 objects among Be stars in the SMC which present short-term photometric variability (P$<$2.5d) with amplitude lower than 0.1 magnitude. This short-term variability is often superimposed to a long-term variation.