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Hydrodynamics of embedded planets’ first atmospheres – III. The role of radiation transport for super-Earth planets

By SpaceRef Editor
August 3, 2017
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Nicolas P. Cimerman, Rolf Kuiper, Chris W. Ormel
(Submitted on 25 Jul 2017)

The population of close-in super-Earths, with gas mass fractions of up to 10% represents a challenge for planet formation theory: how did they avoid runaway gas accretion and collapsing to hot Jupiters despite their core masses being in the critical range of $M_\mathrm{c} \simeq 10 M_\mathrm{\oplus}$? Previous three-dimensional (3D) hydrodynamical simulations indicate that atmospheres of low-mass planets cannot be considered isolated from the protoplanetary disc, contrary to what is assumed in 1D-evolutionary calculations. This finding is referred to as the recycling hypothesis. In this Paper we investigate the recycling hypothesis for super-Earth planets, accounting for realistic 3D radiation hydrodynamics. Also, we conduct a direct comparison in terms of the evolution of the entropy between 1D and 3D geometries. We clearly see that 3D atmospheres maintain higher entropy: although gas in the atmosphere loses entropy through radiative cooling, the advection of high entropy gas from the disc into the Bondi/Hill sphere slows down Kelvin-Helmholtz contraction, potentially arresting envelope growth at a sub-critical gas mass fraction. Recycling, therefore, operates vigorously, in line with results by previous studies. However, we also identify an “inner core” — in size $\approx$ 25% of the Bondi radius — where streamlines are more circular and entropies are much lower than in the outer atmosphere. Future studies at higher resolutions are needed to assess whether this region can become hydrodynamically-isolated on long time-scales.

Comments:    16 pages, 12 figures, accepted for publication at MNRAS
Subjects:    Earth and Planetary Astrophysics (astro-ph.EP)
Cite as:    arXiv:1707.08079 [astro-ph.EP] (or arXiv:1707.08079v1 [astro-ph.EP] for this version)
Submission history
From: Nicolas Patrick Cimerman 
[v1] Tue, 25 Jul 2017 16:40:10 GMT (5203kb,D)

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