Classical Be stars in our Galaxy and the Magellanic Clouds

Abstract

We summarise our studies of the Classical Be (CBe) stars in our Galaxy and in the Large and Small Magellanic Clouds. We studied their properties using optical and near-IR photometry and optical spectroscopy. The CBe stars in the open clusters of the Galaxy were found to belong to two types. B-type stars of spectral type earlier than B1 were found to evolve to CBe phase while the later type stars were found to be born as CBe stars. Thus, CBe phenomenon is unlikely only due to core contraction near the main sequence turn-off. Spectral details of 150 CBe stars were studied, where 48 stars are studied for the first time. This large data set covers CBe stars of various spectral types and ages found in different cluster environments of the northern open clusters. The spectra of 109 candidate CBe stars in the MCs, identified based on photometric variability were studied and the majority showed emission lines suggesting the presence of circumstellar material. We suggest that the photometric variability is a very effective and efficient tool to identify large number of candidate CBe stars and binaries in the Magellanic Clouds.