Hidden Binaries

Massive stars are bright and short lived (for a star). They love to live in couples, that is why many massive stars are found in binary or multiple systems. They are especially important for the formation of live in the Universe as they produce most of the heavy elements, like Carbon, Oxygen, Nitrogen and Iron, from which we are made. To understand how massive stars end their lives, whether they develop into neutron stars or black holes, and to predict how they synthesize different elements, it is important to know about their history and to have proper statistics. Already in the Hydrogen burning stage, the surface of massive stars enriches with Hydrogen burning products like Helium and Nitrogen. There are two ways to transport nuclear processed material from the stellar core to the surface: a) internal currents caused by rotation b) large convective motions caused by mass transfer in a binary system. We know that rotation alone can not explain all patterns of observed surface enhancement. The majority of massive stars are found in binary systems, but after mass transfer these stars appear like single stars, as the mass donor is to faint to be observed. Currently there is no way to tell if the observed surface enrichment comes from mass transfer or rotation. Traditional radial velocity measurements need a lot of observation time and can only detect systems before the mass transfer. I want to change this. My project aims at finding traces in the spectrum that will allow us to separate pre-, and post- interaction binaries from real single stars.