Limb-darkening coefficients from ATLAS9 models

Using up-to-date model atmospheres (Heiter et al. 2002A&A...392..619H) with the turbulent convection approach developed by Canuto, Goldman & Mazzitelli (1996ApJ...473..550C, CGM), quadratic, cubic and square root limb darkening coefficients (LDC) are calculated with a least square fit method for the Stroemgren photometric system. This is done for a sample of solar metallicity models with effective temperatures between 6000 and 8500K and with logg between 2.5 and 4.5.

A comparison is made between these LDC and the ones computed from model atmospheres using the classical mixing length prescription with a mixing length parameter {alpha}=1.25 and {alpha}=0.5. For CGM model atmospheres, the law which reproduces better the model intensity is found to be the square root one for the u band and the cubic law for the v band. The results are more complex for the b and y bands depending on the temperature and gravity of the model.