habitable evaporated cores

The extended pre-main sequence phase of M dwarfs can drive vigorous hydrodynamic escape from their planets. In this paper, I showed how in some cases, small, gas-rich planets can lose their hydrogen envelopes within the habitable zone (HZ) and form (potentially) habitable evaporated cores (HECs). Check out the link at the top for access to the paper.

Figure 1 Regions of parameter space that could be populated by Earth-mass HECs. Terrestrial planets detected today occupying the space to the left of each contour line could be the evaporated cores of gaseous planets. Planets detected to the right of the contour lines have always been terrestrial or gaseous. Dark red lines correspond to the conservative mass loss scenario, in which mass loss is radiation/recombination-limited at high extreme ultraviolet (XUV) flux and energy-limited at low XUV flux. Dark blue lines correspond to mass loss via the energy-limited mechanism only. Different line styles correspond to different eccentricities today. Terrestrial planets detected at higher eccentricity could be evaporated cores at slightly larger orbital separations than planets detected on circular orbits. Note that in the energy-limited regime, all Earth-mass terrestrial planets in the HZ of low-mass M dwarfs could be habitable evaporated cores. At higher stellar mass, HECs are restricted to planets in the inner HZ. In the radiation/recombinationlimited regime, the accessible region of parameter space is smaller, but around the lowest mass M dwarfs HECs are still possible in the conservative HZ.