MAFAGS-OS: New opacity sampling model atmospheres for A, F and G stars

I. The model and the solar flux

Universitäts Sternwarte München, Scheinerstr. 1, 81679 München, Germany

Corresponding author: fug@usm.uni-muenchen.de

Received: 5 January 2004
Accepted: 19 February 2004

Abstract

We present a new opacity sampling model atmosphere code, named MAFAGS-OS. This code, designed for stars reaching from A0 down to G9 on a solar and metal poor main sequence and up to an evolutionary stage represented by the turnoff is introduced in its basic input physics and modelling techniques. Fe I bound-free cross-sections of [CITE] are used and convection is treated according to [CITE]. An -parameter for the efficiency of convection of 0.82 is used as determined by [CITE] from stellar evolution requirements.
Within the process of opacity sampling, special attention is drawn to the matter of line selection. We show that a selection criterion, in which lines are chosen by their opacity weighted relative to the continuous background opacity, is useful and valid. 
The solar model calculated using this new code is shown to fit the measured solar flux distribution. It is also tested against the measured solar colours and leads to and , in good agreement with observation. Comparison with measured centre-to-limb continuum data show only small improvement with respect to opacity-sampling type model atmospheres. This is the first of a series of 2 papers. Paper II will deal with the matter of temperature determination using Balmer lines and the infrared-flux method; furthermore it will present three “standard” stars analysed using this new model.