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Understanding atmospheric escape in close-in exoplanets is critical tointerpreting their evolution. We map out the parameter space over whichphotoevaporation and core-powered mass loss dominate atmospheric escape.Generally, the transition between the two regimes is determined by the locationof the Bondi radius (i.e. the sonic point of core-powered outflow) relative tothe penetration depth of XUV photons. Photoevaporation dominates the loss whenthe XUV penetration depth lies inside the Bondi radius ($R_{XUV}<R_B$) andcore-powered mass-loss when XUV radiation is absorbed higher up in the flow($R_B<R_{XUV}$). The transition between the two regimes occurs at a roughlyconstant ratio of the planet's radius to its Bondi radius, with the exact valuedepending logarithmically on planetary and stellar properties. In general,core-powered mass-loss dominates for lower-gravity planets with higherequilibrium temperatures, and photoevaporation dominates for higher-gravityplanets with lower equilibrium temperatures. However, planets can transitionbetween these two mass-loss regimes during their evolution, and core-poweredmass loss can ``enhance'' photo-evaporation over a significant region ofparameter space. Interestingly, a planet that is ultimately stripped bycore-powered mass-loss has likely only ever experienced core-powered mass-loss.In contrast a planet that is ultimately stripped by photoevaporation could haveexperienced an early phase of core-powered mass-loss. Applying our results tothe observed super-Earth population suggests that it contains significantfractions of planets where each mechanism controlled the final removal of theH/He envelope, although photoevaporation appears to be responsible for thefinal carving of the exoplanet radius-valley.

Mapping out the parameter space for photoevaporation and core-powered mass-loss