Radiative cooling of shocked gas in stellar atmospheres

II. Self-consistent LTE shock wake model with Fe lines and H continua contributions

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

Corresponding author: D. Gillet, gillet@obs-hp.fr

Received: 28 March 2003
Accepted: 13 January 2004

Abstract

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/cm³ for Population I, and less or equal to 10^-12 g/cm³ for Population II). However, for higher densities, 10^-10 g/cm³ 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 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.