EDP Sciences
Free Access
Volume 392, Number 2, September III 2002
Page(s) 619 - 636
Section Stellar atmospheres
DOI https://doi.org/10.1051/0004-6361:20020788

A&A 392, 619-636 (2002)
DOI: 10.1051/0004-6361:20020788

New grids of ATLAS9 atmospheres I: Influence of convection treatments on model structure and on observable quantities

U. Heiter1, 2, F. Kupka1, C. van 't Veer-Menneret3, C. Barban3, 4, W. W. Weiss1, M.-J. Goupil3, W. Schmidt1, 5, D. Katz3 and R. Garrido6

1  Institut für Astronomie, Universität Wien, Türkenschanzstrasse 17, 1180 Vienna, Austria
    e-mail: heiter@astro.univie.ac.at; kupka@astro.univie.ac.at; weiss@astro.univie.ac.at; schmidt@astro.univie.ac.at
2  Department of Astronomy, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7215, USA
    e-mail: ulrike@fafnir.astr.cwru.edu
3  Observatoire de Paris-Meudon, 5 place Jules Janssen, 92195 Meudon Cedex, France
    e-mail: Claude.VantVeer@obspm.fr; Caroline.Barban@obspm.fr; MarieJo.Goupil@obspm.fr; David.Katz@obspm.fr
4  National Solar Observatory, 950 N. Cherry Ave., Tucson, AZ 85719, USA
    e-mail: barban@noao.edu
5  Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching, Germany
    e-mail: wschmidt@mpa-garching.mpg.de
6  Instituto de Astrofisica de Andalucia, C.S.I.C., Apdo. 3004, 18080 Granada, Spain
    e-mail: garrido@iaa.es

(Received 5 February 2002 / Accepted 13 May 2002)

We present several new sets of grids of model stellar atmospheres computed with modified versions of the ATLAS9 code. Each individual set consists of several grids of models with different metallicities ranging from [M/H] = -2.0 to +1.0 dex. The grids range from 4000 to 10 000 K in $T_{\rm eff}$ and from 2.0 to 5.0 dex in $\log{g}$. The individual sets differ from each other and from previous ones essentially in the physics used for the treatment of the convective energy transport, in the higher vertical resolution of the atmospheres and in a finer grid in the ( $T_{\rm eff}$, $\log{g}$) plane. These improvements enable the computation of derivatives of color indices accurate enough for pulsation mode identification. In addition, we show that the chosen vertical resolution is necessary and sufficient for the purpose of stellar interior modelling. To explain the physical differences between the model grids we provide a description of the currently available modifications of ATLAS9 according to their treatment of convection. Our critical analysis of the dependence of the atmospheric structure and observable quantities on convection treatment, vertical resolution and metallicity reveals that spectroscopic and photometric observations are best represented when using an inefficient convection treatment. This conclusion holds whatever convection formulation investigated here is used, i.e. MLT( $\alpha=0.5$), CM and CGM are equivalent. We also find that changing the convection treatment can lead to a change in the effective temperature estimated from Strömgren color indices from 200 to 400 K.

Key words: stars: atmospheres -- stars: fundamental parameters -- stars: variables $\delta$ Scuti stars -- convection

Offprint request: U. Heiter, heiter@astro.univie.ac.at

© ESO 2002