Binary Stellar Interactions in Diverse Fields of Astrophysics

Binary interactions certainly happen to stars. Interacting stars can lose or gain mass, forever altering their evolutionary histories. It is less evident that these processes leave a footprint in almost all fields of astrophysics. In this talk, I will give a few examples of such footprints. Red giants that have lost mass due to their companions can leave behind small helium-burning stars - their former cores - which appear as bright UV sources in the sky. The orbits of such systems clearly show imprints from the Galactic chemical history. In a closely related population, the cores of red giants stripped by a binary companion may end up in the instability strip, producing RR Lyrae stars relevant to the variable stellar community and cosmologists alike. Double white dwarfs, too, before merging, have a short interaction phase where the larger white dwarf loses mass. As we recently showed, this lost mass ends up in the well-observed early lightcurves of supernovae produced by double white dwarf mergers, informing us about their progenitors. I will conclude with a bold claim - any field of astronomy contains binary interaction signatures.