The origin of hydrogen around HD 209458b

Etangs, A. Lecavelier des; Vidal-Madjar, A.; Desert, J. -M.

The origin of hydrogen around HD 209458b

Authors

Etangs, A. Lecavelier des

Vidal-Madjar, A.

Desert, J. -M.

Description

Using numerical simulation, Holmstrom et al. (2008) proposed a plausible alternative explanation of the observed Lyman-alpha absorption that was seen during the transit of HD 209458b (Vidal-Madjar et al. 2003). They conclude that radiation pressure alone cannot explain the observations and that a peculiar stellar wind is needed. Here we show that radiation pressure alone can in fact produce the observed high-velocity hydrogen atoms. We also emphasize that even if the stellar wind is responsible for the observed hydrogen, to have a sufficient number of atoms for charge exchange with stellar wind, the energetic neutral atom (ENA) model also needs a significant escape from the planet atmosphere of similar amplitude as quoted in Vidal-Madjar et al.(2003).
Brief Communications Arising, Nature 456, E1 (2008) (2008Natur.456....1L)