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Issue A&A
Volume 458, Number 2, November I 2006
Page(s) L13 - L16
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20066093



A&A 458, L13-L16 (2006)
DOI: 10.1051/0004-6361:20066093

Letter

Stellar X-ray heating of planet atmospheres

C. Cecchi-Pestellini1, A. Ciaravella2 and G. Micela2

1  INAF - Osservatorio Astronomico di Cagliari, Strada 54, Loc. Poggio dei Pini, 09012 Capoterra (CA), Italy
    e-mail: ccp@ca.astro.it
2  INAF - Osservatorio Astronomico di Palermo, Piazza Parlamento 1, 90134 Palermo, Italy
    e-mail: ciarave@astropa.unipa.it, giusi@astropa.unipa.it

(Received 24 July 2006 / Accepted 28 August 2006)

Abstract
Aims.To investigate the effects of the stellar X-ray irradiation on planet atmospheres, we study the X-ray transfer and energy deposition in a hydrogen rich gas.
Methods.We construct an accurate X-ray transfer model taking both photoionization and Compton scattering into account; the electron energy deposition is followed by tracking the discrete exchange processes between electrons and the gas mixture.
Results.Exospheric heating rates are derived as functions of the pressure in model atmospheres using a wide range of X-ray luminosity, spectral hardness representative of different stellar ages, and distances from the parent star. The computed heating rates suggest that X-ray irradiation might be an important heating source in planetary exospheres even at large distances from the parent star.


Key words: planetary systems -- X-rays: stars -- radiative transfer



© ESO 2006


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