Planets and X-rays: a radiation diet

Source: arXiv


According to theory, high energy emission from the coronae of cool stars can
severely erode the atmosphere of orbiting planets. To test the long term
effects of the erosion we study a large sample of planet-hosting stars observed
in X-rays. The results reveal that massive planets (Mp sin i > 1.5 Mj) may
survive only if exposed to low accumulated coronal radiation. The planet HD
209458 b might have lost more than 1 Mj already, and other cases, like tau Boo
b, could be losing mass at a rate of 3.4 Earth masses per Gyr. The strongest
erosive effects would take place during the first stages of the stellar life,
when the faster rotation generates more energetic coronal radiation. The
planets with higher density seem to resist better the radiation effects, as
foreseen by models. Current models need to be improved to explain the observed
distribution of planetary masses with the coronal radiation received.

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