To Be or not to Be ?

Be stars are near Main Sequence B-type stars presenting Balmer-line emission. The widely admitted scenario for these objects is a star rotating close to the critical limit surrounded by a disk, this disk being the feature seen in emission. The Be star β Cep, though, was challenging this scenario because it is a known slow rotator. In a letter published in the latest A&A issue, four researchers put an end to this mystery by showing that the emission feature comes not from β Cep itself but from a 3.4 magnitudes fainter companion that could be rotating at critical limit.