Long-term Evolution of Massive-star Post-common-envelope Circumbinary Disks and the Environments of Fast Luminous Transients

Abstract

If the envelope of a massive star is not entirely removed during common envelope (CE) interaction with an orbiting compact (e.g., black hole (BH) or neutron star (NS)) companion, the residual bound material eventually cools, forming a centrifugally supported disk around the binary containing the stripped He core. We present a time-dependent height-integrated model for the long-term evolution of post-CE circumbinary disks (CBDs), accounting for mass and angular momentum exchange with the binary, irradiation heating by the He core, and photoevaporation wind mass loss. A large fraction of the CBD’s mass is accreted prior to its outwards viscous spreading and wind dispersal on a timescale of ∼10 ^4 –10 ^5 yr, driving significant orbital migration, even for disks containing ∼10% of the original envelope mass. Insofar that the CBD lifetime is comparable to the thermal (and, potentially, nuclear) timescale of the He core, over which a second mass-transfer episode onto the companion can occur, the presence of the CBD could impact the stability of this key phase. Disruption of the core by the BH/NS would result in a jetted energetic explosion into the dense gaseous CBD (≲10 ^15 cm) and its wind (≳10 ^16 cm), consistent with the environments of luminous fast blue optical transients like AT2018cow. Evolved He cores that undergo core collapse still embedded in their CBD could generate Type Ibn/Icn supernovae. Thousands of dusty wind-shrouded massive-star CBDs may be detectable as extragalactic luminous infrared sources with the Roman Space Telescope; synchrotron radio nebulae powered by the CBD-fed BH/NS may accompany these systems.

Keywords

• Common envelope evolution
• Common envelope binary stars
• Supernovae
• X-ray transient sources
• Stellar accretion disks
• Protoplanetary disks