Different channels for the origin of the Be phenomenon have been proposed. One of them is based on binarity, proposing that Be stars are the mass gainers in post-mass-transfer binary systems. Apart from gaining mass, the stars also gained angular momentum, spinning them up to almost critical rotation rates. If the binary channel is the dominating one in the formation of massive Be stars, two clear and testable predictions emerge:

• there should be a lack of Be stars in close binary systems with main-sequence (MS) companions
• Be stars in binaries should have exotic companions such as envelope-stripped Helium stars, neutron stars and black holes

In a literature study of a sample of ~300 massive Be stars (with spectral types B1.5 and earlier) in the Milky Way, we found that there is a clear lack of reported Be stars in binary systems with close main-sequence companions. While the sample is inhomogeneous, this gives a first hint that the binary channel might be dominating in the formation of massive Be stars.

We confirm that there is a surprisingly large number of classical Be stars, that is rapidly rotating stars that display characteristics Balmer emission lines arising in a circumstellar decretion disk. Based on their position in the color-magnitude diagram, they are prime candidates for binary interaction products. Using the multi-epoch nature of the MUSE observations, we identify binary systems in the cluster. We find that the current binary fraction in NGC 330 is significantly lower than in young stellar cluster.