An upper limit for the mass los rate of HD 209458b

SCHNEITER, E. M.; VELAZQUEZ, P. F.; BLANCO-CANO, X.; ESQUIVEL, A.; RAGA, A. C.

Acapulco, Guerrero, Mexico

Congreso; American Geophysical Union, Spring Meeting 2007; 2007

AGU

HD 209458b is a Jovian like planet orbiting around a star with similar characteristic to the Sun. It was discovered by its repeated transit across the stellar disk. The orbital period is 3.5 days, with a mean distance to the star of 0.045 AU (closer than Mercury to the Sun in our system). The peculiar characteristic of this system is that the planet shows an apparent larger size when observed in Lyman α (1214-1217 A) than in optical wavelength (Na I). This discrepancy is thought to be due to the existence of an extended upper atmosphere or wake (comet like wake). In this work we present 3D numerical simulations of this system (done with the adaptive grid Yguazú-a code), and study the absorption produced by this extended atmosphere. The atmosphere is modelled as a wind outgoing from the surface of the planet at velocities of the order of the escape velocity (60 km s-1). Four runs where carried out considering different mass loss rates for the planet in the range [ ]MSUNyr-1. By comparing the model with the observations, we found an upper limit for the mass loss rate of HD 209458b (previous works only found a lower limit. We compare HD 209458b characteristics with solar system planets.