Mike M

The common envelope (CE) binary interaction happens when an evolving, expanding star, such as a subgiant, a red giant branch (RGB), an asymptotic giant branch (AGB), or a red supergiant star, transfers gas to a compact companion, either a lower mass main-sequence star or a white dwarf, neutron star, or black hole. Mass transfer tends to be unstable and leads to the formation of an extended CE surrounding the giant’s core and the companion.