Common envelopes in massive stars: Towards the role of radiation pressure and recombination energy in ejecting red supergiant envelopes

Understand

We perform 3D hydrodynamical simulations of a common-envelope event involving a 12 solar mass red supergiant donor.

• Massive stars are expected to be qualitatively different from low-mass stars as their envelopes have significant support from radiation pressure, which increases both the final separation and amount of mass ejected through the common-envelope interaction.
• We perform adiabatic simulations that include radiation energy through the equation of state, which results in ejecting 60 per cent more mass (up to two thirds of the total envelope mass becoming unbound, or more) and yield a 10 per cent larger final separation compared to simulations that assume an ideal gas.
• When also including recombination energy, we find that at least three quarters of the envelope, and possibly the entire envelope, may be unbound.