Massive Oe/Be stars at low metallicity: Candidate progenitors of long GRBs?
At low metallicity the B-type stars rotate faster than at higher metallicity, typically in the SMC. As a consequence, it was expected a larger number of fast rotators in the SMC than in the Galaxy, in particular more Be/Oe stars. With the ESO-WFI in its slitless mode, the SMC open clusters were examined and an occurence of Be stars 3 to 5 times larger than in the Galaxy was found. The evolution of the angular rotational velocity seems to be the main key on the understanding of the specific behaviour and of the stellar evolution of such stars at different metallicities. With the results of this WFI study and using observational clues on the SMC WR stars and massive stars, as well as the theo…
Album: A Tool for the Analysis of Slitless Spectra and its Application to ESO WFI Data
ALBUM is a general-purpose tool to visualize and screen large amounts of slitless spectra∈dex slitless spectra. It was developed for a search for emission-line stars in SMC and LMC clusters. The observations were obtained with ESO’s Wide Field Imager (WFI∈dexWFI) and comprise ~8 million low-resolution spectra. The tool as well as the results of its application to the SMC part of the database are presented. The inferred frequency of Be stars is compared to the one in the higher-metallicity environment of the Milky Way.