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. 2015 Feb 1;15(2):119–143. doi: 10.1089/ast.2014.1231

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Copyright 2015, Mary Ann Liebert, Inc.

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FIG. 1. — Evolution of the XUV flux received by planets close to the inner edge of the HZ orbiting 0.1, 0.2, and 0.3 M_⊙ M dwarfs, scaled to that received by present Earth, _⊕=4.64 erg/cm²/s. Solid lines correspond to the model adopted in this paper, where fluxes are calculated using the stellar evolution model of Baraffe et al. (1998) and the XUV evolution of Ribas et al. (2005), assuming a saturation time t_sat of 1 Gyr and a saturation fraction of 10⁻³. Dashed lines correspond to the empirical model of Penz and Micela (2008), who assume a single XUV luminosity for all M dwarfs; see text for a discussion. The evolution of the flux at Earth is shown for reference as a black line. The dot corresponds to the earliest time for which the study of Ribas et al. (2005) has data for solar-type stars and is approximately equal to the saturation time for the Sun; it is also roughly the formation time for Earth.

Inline graphic — Evolution of the XUV flux received by planets close to the inner edge of the HZ orbiting 0.1, 0.2, and 0.3 M_⊙ M dwarfs, scaled to that received by present Earth, _⊕=4.64 erg/cm²/s. Solid lines correspond to the model adopted in this paper, where fluxes are calculated using the stellar evolution model of Baraffe et al. (1998) and the XUV evolution of Ribas et al. (2005), assuming a saturation time t_sat of 1 Gyr and a saturation fraction of 10⁻³. Dashed lines correspond to the empirical model of Penz and Micela (2008), who assume a single XUV luminosity for all M dwarfs; see text for a discussion. The evolution of the flux at Earth is shown for reference as a black line. The dot corresponds to the earliest time for which the study of Ribas et al. (2005) has data for solar-type stars and is approximately equal to the saturation time for the Sun; it is also roughly the formation time for Earth.