Cool and Luminous Outbursts from Merging Binary Stars
Ondrej Pejcha

Many binary stars pass through a phase of dramatic energy, mass, and angular momentum loss. The existing theoretical uncertainties in this short-lived interaction phase significantly affect our understanding of the binary evolution pathways and their rates, including formation of close binaries composed of black holes, neutron stars and white dwarfs. The discovery of V1309 Sco, a contact binary with rapidly decreasing orbital period followed by an outburst, recently established a connection between these astrophysically critical, catastrophic interactions and a group of astronomical transients characterized by their red color and the luminosity in the gap between novae and supernovae. I will present an exploration of the dynamics of outflows from mass-losing binary stars and the associated menagerie of transients. I will interpret the unprecedentedly detailed pre-merger data on V1309 Sco and argue that these transients can provide a fresh observational input into the open problem of violent binary interactions.