© ESO 2021Lampón, M.López Puertas, M.Czesla, S.Sánchez López, A.Lara, L. M.Salz, M.Sanz Forcada, J.Molaverdikhani, K.Quirrenbach, A.Pallé, E.Caballero, J. A.Henning, T.Nortmann, L.Amado, P. J.Montes, D.Reiners, A.Ribas, I.Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737Centro de Excelencia Científica Severo Ochoa Instituto de Astrofísica de Andalucía , SEV-2017-0709Centro de Excelencia Científica Severo Ochoa Instituto de Astrofísica de Canarias, SEV-2015-05482022-02-162022-02-162021-04-23Astronomy and Astrophysics 648: L7(2021)0004-6361https://www.aanda.org/articles/aa/full_html/2021/04/aa40423-21/aa40423-21.htmlhttp://hdl.handle.net/20.500.12666/630Hydrodynamic 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 a helium I triplet at 10 830 Å and Lyα 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.engAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttps://creativecommons.org/licenses/by/4.0/Planets and satellites: atmospheresPlanets and satellites: gaseous planetsPlanets and satellites: individual: GJ 3470 bPlanets and satellites: individual: HD 209458 bPlanets and satellites: individual: HD 189733 binfo:eu-repo/semantics/article10.1051/0004-6361/2021404231432-0746http://dx.doi.org/10.13039/501100003339http://dx.doi.org/10.13039/501100011011http://dx.doi.org/10.13039/501100001659http://dx.doi.org/10.13039/501100011033http://dx.doi.org/10.13039/501100003329http://dx.doi.org/10.13039/501100002809http://dx.doi.org/10.13039/501100000781info:eu-repo/semantics/openAccess