© ESO 2021Lampón, M.López Puertas, M.Czesla, S.Sánchez López, A.Lara, L. M.Salz, M.Sanz-Forcada, JorgeMolaverdikhani, 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