Common Envelope Mass Ejection in Evolved Stars: Modeling the Dust Emission from Post-RGB Stars in the LMC

Abstract Common envelope (CE) systems are the result of Roche lobe overflow in interacting binaries. The subsequent evolution CE, its ejection, and formation dust ejecta while primary is on red giant branch (RGB) gives rise to a recently identified evolutionary class—dusty post-RGB stars. Their spectral energy distributions (SEDs) suggest that their mass-ejecta similar dusty post-asymptotic (post-AGB) We have modeled SEDs select sample post-AGB stars Large Magellanic Cloud, quantified total mass (and gas assuming gas-to-dust ratio) disks shells set constraints grain compositions sizes. find shell masses post-RGBs generally less than those post-AGBs, with caveat substantial amount both types objects may lie cold, extended shells. Our models circumstellar disks, when present, geometrically thick structures opening angle, consistent numerical simulations CE (CEE). Comparison our model predictions production during CEE RGB occurred near or at tip for sources. A surprising some harbor carbon-rich dust, believed form C/O > 1, e.g., following triple-alpha nucleosynthesis third dredge-up events AGB This anomaly strengthens hypothesis born binary systems.