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arXiv · 2104.08832

Evidence of energy-, recombination-, and photon-limited escape regimes in giant planet H/He atmospheres

M. Lampón·M. López-Puertas·S. Czesla·A. Sánchez-López·L. M. Lara·M. Salz·J. Sanz-Forcada·K. Molaverdikhani·A. Quirrenbach·E. Pallé·J. A. Caballero·Th. Henning·L. Nortmann·P. J. Amado·D. Montes·A. Reiners·I. Ribas
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Abstract

Hydrodynamic escape is the most efficient atmospheric mechanism of planetary mass loss and has a large impact on planetary evolution. Three hydrodynamic escape regimes have been identified theoretically: energy-limited, recombination-limited, and photon-limited. However, no evidence of these regimes had been reported until now. Here, we report evidence of these three regimes via an analysis of helium I triplet at 10830 angstroms and Ly-$\alpha$ absorption involving a 1D hydrodynamic model that allows us to estimate hydrogen recombination and advection rates. In particular, we show that HD 209458 b is in the energy-limited regime, HD 189733 b is in the recombination-limited regime, and GJ 3470 b is in the photon-limited regime. These exoplanets can be considered as benchmark cases for their respective regimes.

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M. Lampón, M. López-Puertas, S. Czesla, A. Sánchez-López, L. M. Lara, M. Salz, J. Sanz-Forcada, K. Molaverdikhani, A. Quirrenbach, E. Pallé, J. A. Caballero, Th. Henning, L. Nortmann, P. J. Amado, D. Montes, A. Reiners, I. Ribas. 2021-04-18. Evidence of energy-, recombination-, and photon-limited escape regimes in giant planet H/He atmospheres. https://doi.org/10.1051/0004-6361/202140423

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