Publication Date:
2016-06-17
Description:
For the hot exoplanets CoRoT-24b and CoRoT-24c, observations have provided transit radii R T of 3.7 ± 0.4 R and 4.9 ± 0.5 R , and masses of ≤5.7 M and 28 ± 11 M , respectively. We study their upper atmosphere structure and escape applying an hydrodynamic model. Assuming R T R PL , where R PL is the planetary radius at the pressure of 100 mbar, we obtained for CoRoT-24b unrealistically high thermally driven hydrodynamic escape rates. This is due to the planet's high temperature and low gravity, independent of the stellar EUV flux. Such high escape rates could last only for 〈100 Myr, while R PL shrinks till the escape rate becomes less than or equal to the maximum possible EUV-driven escape rate. For CoRoT-24b, R PL must be therefore located at 1.9–2.2 R and high altitude hazes/clouds possibly extinct the light at R T . Our analysis constraints also the planet's mass to be 5–5.7 M . For CoRoT-24c, R PL and R T lie too close together to be distinguished in the same way. Similar differences between R PL and R T may be present also for other hot, low-density sub-Neptunes.
Print ISSN:
1745-3925
Electronic ISSN:
1745-3933
Topics:
Physics
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