Cool Stars 14 - Submitted Abstract # 281
This version created on 05 October 2006

Host star influence on the atmospheric evolution of 'Hot Neptunes'


Thomas Penz, INAF - Osservatorio Astronomico di Palermo
Nikolai Erkaev, Institute for Computational Modelling - Russian Academy of Sciences
Cesare Cecchi-Pestellini, INAF - Osservatorio Astronomico di Cagliari
Yuri Kulikov, Polar Geophysical Institute - Russian Academy of Sciences
Helmut Lammer, Space Research Institute - Austrian Academy of Sciences
Angela Ciaravella, INAF - Osservatorio Astronomico di Palermo
Giuseppina Micela, INAF - Osservatorio Astronomico di Palermo
Daniel Langmayr, Space Research Institute - Austrian Academy of Sciences
Helfried Biernat, Space Research Institute - Austrian Academy of Sciences

Astrophysical observations of young stars (T-Tauri, post T-Tauri and
even young main sequence stars) indicate much larger X-ray and EUV
fluxes than stars with the age of our present Sun.  Because giant
planet formation occurs relatively fast, one can expect that the early
high radiation flux in the short wavelengths will have a great impact
at the atmospheres of 'Hot Neptunes'.  We discuss the physical
conditions when hydrodynamic 'blow off' can occur and apply an
efficient time-dependent numerical algorithm which is able to solve
the system of hydrodynamic equations straight through the transonic
point of a flow for studying planetary winds.  The mass and energy
fluxes are calculated as functions of the absorbed energy in the upper
atmosphere.  We show that at very high X-ray and EUV fluxes the
incoming stellar energy is converted into kinetic and thermal energy
of the planetary hydrogen wind.  Additionally, we discuss if 'Hot
Neptunes' might be the remnants of evaporated 'Hot Jupiters'.

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