EDP Sciences
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Volume 420, Number 3, June IV 2004
Page(s) 1047 - 1059
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20040122

A&A 420, 1047-1059 (2004)
DOI: 10.1051/0004-6361:20040122

Radiative cooling of shocked gas in stellar atmospheres

II. Self-consistent LTE shock wake model with Fe lines and H continua contributions
A. B. Fokin1, 2, G. Massacrier3 and D. Gillet4

1  Institute of Astronomy of the Russian Academy of Sciences, 48 Pjatnitskaya Str., Moscow 109017, Russia
2  Isaak Newton Institute Moscow Branch
3  CRAL, UMR 5574 du CNRS, École Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France
4  Observatoire de Haute Provence, CNRS, 04870 Saint Michel l'Observatoire, France

(Received 28 March 2003 / Accepted 13 January 2004)

The hot radiative shock wake structure, including the radiative cooling due to H continuum and the Fe lines under typical conditions of stellar atmospheres, is considered. The proposed iterative method of calculation is stable and gives the temperature profile with a good precision (2-5%). The dependence of the wake structure on the preshock parameters is studied, and the line cooling is compared to that of continua in a more self-consistent way. We confirm that the iron cooling is very efficient for low preshock densities (less or equal to 10-11 g/cm 3 for Population I, and less or equal to 10-12 g/cm 3 for Population II). However, for higher densities, 10-10 g/cm 3 and more, especially for the Population II composition, the line cooling becomes secondary with respect to the continuum. As a consequence, the iron cooling is expected to be efficient for pulsating stars having low R/M ratios, like classical Cepheids or RR Lyrae, and much less efficient for W Vir, RV Tauri and Miras. This is discussed in view of the well-known drastic difference in the observed emission features between these two stellar groups.

Key words: shock waves -- stars: oscillations -- stars: atmospheres

Offprint request: D. Gillet, gillet@obs-hp.fr

© ESO 2004