A temperature correction method for expanding atmospheres
W.-R. Hamann and G. Gräfener
Model atmospheres form the basis for the interpretation of stellar spectra. A major problem in those model calculations is to establish the temperature stratification from the condition of radiative equilibrium. Dealing with non-LTE models for spherically expanding atmospheres of Wolf-Rayet stars, we developed a new temperature correction method. Its basic idea dates back to 1955 when it was proposed by Unsöld for grey, static and plane-parallel atmospheres in LTE. The equations were later generalized to the non-grey case by Lucy. In the present paper we furthermore drop the Eddington approximation, proceed to spherical geometry and allow for expansion of the atmosphere. Finally the concept of an "approximate lambda operator" is employed to speed up the convergence. Tests for Wolf-Rayet type models demonstrate that the method works fine even in situations of strong non-LTE.
The full article is available as PostScript file via anonymous ftp.
user: anonymous or ftp; Password: your e-mail address;
file: pub/wrhamann/unsoeld-lucy.ps (312 KB uncompressed) or unsoeld-lucy.ps.gz (100 KB compressed).