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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. Gillet41 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)
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/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