Limb-darkening coefficients of illuminated atmospheres. I. Results for illuminated line-blanketed models with 3 700 K < T_eff < 7 000 K

The effect of mutual illumination in a close binary on the limb-darkening coefficients is studied using the UMA (Uppsala Model Atmosphere) code in convective line-blanketed atmospheres illuminated by line-blanketed fluxes, for 3 700 K<T_eff<7 000 K and 7 000 K<T_h<12 000 K. The results show that the limb-darkening coefficients of illuminated atmospheres are significantly different from the non-illuminated ones and mostly depend on four parameters: the amount of incident energy, the illumination direction, the effective temperature of the illuminated star and the temperature of the illuminating one. We present bolometric, monochromatic and passband specific coefficients and we give, for the latter, analytical expressions in order to easily account for the effect in light curve synthesis programs. Tables 1, 2 and 3 will be also accessible in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html