Contact binaries: a window to a long union of massive stars

We live in an exciting era of astrophysics, where a huge swell of data from the ongoing LIGO-VIRGO mission and the upcoming LSST survey will soon be at our doorstep. To be prepared for what these missions will observe, we need to first understand the source of these cosmic phenomena— massive stars. In this talk, I will introduce you to one of the most peculiar configurations of massive binary stars called the `contact phase’, where both stars of the binary system overflow their Roche lobes simultaneously and transfer mass to one another.  Although only a few massive contact binaries have been recorded, these are the only observable gateways we have in order to study one of the most puzzling and crucial stellar phenomena— mergers. In this talk, I will present the results of the first theoretical study of massive contact binaries, based on 1D simulations of binary stars in the Milky Way and the Magellanic Clouds. By comparing the theoretical distributions we thus obtain with their observed counterparts, we gain an insight not only in to the workings of contact binaries, but also in to the fundamental physics of stellar interiors.