EDP Sciences
Free access
Volume 412, Number 1, December II 2003
Page(s) 241 - 248
Section Formation and evolution of planetary systems
DOI http://dx.doi.org/10.1051/0004-6361:20031405

A&A 412, 241-248 (2003)
DOI: 10.1051/0004-6361:20031405

The limb-darkening for spherically symmetric NextGen model atmospheres: A-G main-sequence and sub-giant stars

A. Claret1 and P. H. Hauschildt2

1  Instituto de Astrofísica de Andalucía, CSIC, Apartado 3004, 18080 Granada, Spain
2  Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
    e-mail: Peter.Hauschildt@hs.uni-hamburg.de

(Received 4 June 2003 / Accepted 29 August 2003 )

We compute passband-integrated specific intensities for spherically symmetric models generated with the PHOENIX code. The models cover the range $5000~{\rm K} \le T_{\rm eff}\le 10\,000$ K with surface gravities between 3.5 and 5.5, in steps of 0.5. The adopted mixing-length parameter is 2.0 pressure scale heights, while the microturbulent velocity is 2.0 km s -1. The calculations were carried out for four photometric systems: Strömgren, Johnson, Geneva and Walraven, completing 24 filters. The series introduced by Claret (2000) and a new bi-parametric (exponential) law are shown to be able to describe the intensity distribution of spherical models with acceptable  $\sigma$. Simple limb-darkening laws do not produce accurate fits to the computed radiation fields. On the other hand, the concept of "quasi" spherical models is introduced and we present the corresponding limb-darkening coefficients for the most commonly adopted limb-darkening laws for the same filters.

Key words: stars: atmospheres -- stars: binaries: eclipsing

Offprint request: A. Claret, claret@iaa.es

© ESO 2003