Convection Reconciles the Difference in Efficiencies Between Low-Mass and High-Mass Common Envelopes. (arXiv:2203.06091v1 [astro-ph.SR])

Convection Reconciles the Difference in Efficiencies Between Low-Mass and High-Mass Common Envelopes. (arXiv:2203.06091v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Wilson_E/0/1/0/all/0/1">E. C. Wilson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nordhaus_J/0/1/0/all/0/1">J. Nordhaus</a>

The formation pathways for gravitational-wave merger sources are predicted to
include common envelope (CE) evolution. Observations of high-mass post-common
envelope binaries suggest that energy transfer to the envelope during the CE
phase must be highly efficient. In contrast, observations of low-mass post-CE
binaries indicate energy transfer during the CE phase must be highly
inefficient. Convection, a process present in low-mass and high-mass stars,
naturally explains this dichotomy. Using observations of Wolf-Rayet binaries,
we study the effects of convection and radiative losses on the predicted final
separations of high-mass common envelopes. Despite robust convection in massive
stars, the effect is minimal as the orbit decays well before convection can
transport the liberated orbital energy to the surface. In low-mass systems,
convective transport occurs faster then the orbit decays, allowing the system
to radiatively cool thereby lowering the efficiency. The inclusion of
convection reproduces observations of low-mass and high-mass binaries and
remains a necessary ingredient for determining outcomes of common envelopes.

The formation pathways for gravitational-wave merger sources are predicted to
include common envelope (CE) evolution. Observations of high-mass post-common
envelope binaries suggest that energy transfer to the envelope during the CE
phase must be highly efficient. In contrast, observations of low-mass post-CE
binaries indicate energy transfer during the CE phase must be highly
inefficient. Convection, a process present in low-mass and high-mass stars,
naturally explains this dichotomy. Using observations of Wolf-Rayet binaries,
we study the effects of convection and radiative losses on the predicted final
separations of high-mass common envelopes. Despite robust convection in massive
stars, the effect is minimal as the orbit decays well before convection can
transport the liberated orbital energy to the surface. In low-mass systems,
convective transport occurs faster then the orbit decays, allowing the system
to radiatively cool thereby lowering the efficiency. The inclusion of
convection reproduces observations of low-mass and high-mass binaries and
remains a necessary ingredient for determining outcomes of common envelopes.

http://arxiv.org/icons/sfx.gif