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Astron. Astrophys. 326, 277-286 (1997)

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Spherically symmetric model atmospheres using approximate lambda operators

III. The equations of statistical equilibrium with occupation probabilities

Jií Kubát

Astronomický ústav, Akademie vd eské republiky, 251 65 Ondejov, Czech Republic

Received 7 March 1997 / Accepted 22 April 1997


The occupation probability formalism is implemented into the equations of statistical equilibrium. The equations and corresponding expressions for rates are presented in detail. The improved equations are used for the calculation of sample spherically symmetric NLTE model atmospheres. The difference between this formalism and standard cutoff formula is studied for pure hydrogen atmospheres. It is small for main-sequence and sdO stars. However, a larger difference is found for white dwarfs.

Key words: stars: atmospheres – atomic processes – methods: numerical

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© European Southern Observatory (ESO) 1997

Online publication: April 20, 1998