Contributed Talk - Splinter Stellar

Friday, 25 September 2020, 10:14   (virtual room M)

Formation of sdB stars in common envelope interaction with substellar companions

F. K. Röpke, M. Kramer, F.R. N. Schneider, S. T. Ohlmann, S. Geier, V. Schaffenroth, R. Pakmor
HITS; ZAH Heidelberg University: ARI, ITA; MPCDF Garching, Potsdam University, MPA Garching

Common envelope (CE) phases in binary systems, where the primary star reaches the tip of the red giant branch, have been suggested as a formation scenario for hot subluminous B-type (sdB) stars. Some of these are observed in binary systems with very low-mass companions. In hydrodynamical CE simulations with the moving-mesh code AREPO, we test whether such low-mass objects can successfully unbind the envelope. We find this to be the case for companion masses down to the brown dwarf mass range if the release of recombination energy is taken into account and a local thermalization of that energy is assumed. This underpins the role CE phases can play in the formation of sdB stars.