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  5. Mapping out the parameter space for photoevaporation and core-powered mass-loss
 
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Mapping out the parameter space for photoevaporation and core-powered mass-loss
File(s)
stad3972.pdf (2.1 MB)
Published version
Author(s)
Owen, James E
Schlichting, Hilke E
Type
Journal Article
Abstract
Understanding atmospheric escape in close-in exoplanets is critical to interpreting their evolution. We map out the parameter space over which photoevaporation and core-powered mass-loss dominate atmospheric escape. Generally, the transition between the two regimes is determined by the location of the Bondi radius (i.e. the sonic point of core-powered outflow) relative to the penetration depth of extreme ultra-violet (XUV) photons. Photoevaporation dominates the loss when the XUV penetration depth lies inside the Bondi radius (RXUV < RB) and core-powered mass-loss when XUV radiation is absorbed higher up in the flow (RB < RXUV). The transition between the two regimes occurs at a roughly constant ratio of the planet’s radius to its Bondi radius, with the exact value depending logarithmically on planetary and stellar properties. In general, core-powered mass-loss dominates for lower gravity planets with higher equilibrium temperatures, and photoevaporation dominates for higher gravity planets with lower equilibrium temperatures. However, planets can transition between these two mass-loss regimes during their evolution, and core-powered mass-loss can ‘enhance’ photoevaporation over a significant region of parameter space. Interestingly, a planet that is ultimately stripped by core-powered mass-loss has likely only ever experienced core-powered mass-loss. In contrast, a planet that is ultimately stripped by photoevaporation could have experienced an early phase of core-powered mass-loss. Applying our results to the observed super-Earth population suggests that it contains significant fractions of planets where each mechanism controlled the final removal of the H/He envelope, although photoevaporation appears to be responsible for the final carving of the exoplanet radius valley.
Date Issued
2024-02
Date Acceptance
2023-12-21
Citation
Monthly Notices of the Royal Astronomical Society, 2024, 528 (2), pp.1615-1629
URI
http://hdl.handle.net/10044/1/108978
URL
http://dx.doi.org/10.1093/mnras/stad3972
DOI
https://www.dx.doi.org/10.1093/mnras/stad3972
ISSN
0035-8711
Publisher
Oxford University Press
Start Page
1615
End Page
1629
Journal / Book Title
Monthly Notices of the Royal Astronomical Society
Volume
528
Issue
2
Copyright Statement
© 2023 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
License URL
https://creativecommons.org/licenses/by/4.0/
Identifier
http://dx.doi.org/10.1093/mnras/stad3972
Publication Status
Published
Date Publish Online
2023-12-23
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