2011A&A...529A..75C

The complex physics of close binary stars is made even more challenging by the proximity effects that affect it. Understanding the influence of these proximity effects is one of the most important tasks in theoretical stellar astrophysics. It is crucial to know how the specific intensity is distributed over the stellar disk for a correct modelling of the light curves of eclipsing binaries and planetary transits. To provide theoretical input for light curve modelling codes, we present new calculations of gravity- and limb-darkening coefficients for a wide range of effective temperatures, gravities, metallicities, and microturbulent velocities. We computed limb-darkening coefficients for several atmosphere models, which cover the transmission curves of the Kepler, CoRoT, and Spitzer space missions as well as more widely used passbands (Stroemgren, Johnson-Cousins, Sloan). In addition to these computations, which were made adopting the least-square method, we also performed calculations for the bi-parametric approximations by adopting the flux conservation method to provide users with an additional tool to estimate the theoretical error bars. To facilitate the modelling of the effects of tidal and rotational distortions, we computed the gravity-darkening coefficients y(λ) using the same models of stellar atmospheres as for the limb-darkening. Compared to previous work, a more general differential equation was used, which now takes into account local gravity variations and the effects of convection. The limb-darkening coefficients were computed with a higher numerical resolution (100 µ points instead of 15 or 17, as is often used in the ATLAS models), and five equations were used to describe the specific intensities (linear, quadratic, root-square, logarithmic, and a 4-coefficient law). Concerning the gravity-darkening coefficients, the influence of the local gravity on y(λ) is shown as well as the effects of convection, which turn out to be very significant for cool stars. The results are tabulated for logg's ranging from 0.0 to 5.0,-5.0≤log[M/H]≤+1,2000K≤T_eff≤50000K and for five values of the microturbulent velocity. ATLAS and PHOENIX plane-parallel atmosphere models were used for all computations.