Theoretical gravity and limb-darkening coefficients for the MOST satellite photometric system

Abstract

Aims. We present new calculations of limb and gravity-darkening coefficients to be used as input in many fields of stellar physics such as synthetic light curves of double-lined eclipsing binaries and planetary transits, studies of stellar diameters or line profiles in rotating stars. Methods. We compute the limb-darkening coefficients specifically for the photometric system of the satellite MOST (Microvariability and Oscillations in STars). All computations were performed by adopting the least-square method, but for completeness we also performed calculations for the linear and bi-parametric approaches by adopting the flux conservation method. The passband gravitydarkening coefficients y(λ) were computed by adopting a more general differential equation, which also takes the effects of convection into account. Results. We used two stellar atmosphere models: ATLAS (plane-parallel) and PHOENIX (spherical and quasi-spherical). We adopted six laws to describe the specific intensity distribution: linear, quadratic, square root, logarithmic, exponential, and a more general one with four terms. The covered ranges of Teff ,l ogg, metallicities, and microturbulent velocities are (1500–50 000 K, 0–5.5, −5.0–+1.0, 0–8 km s −1 ), respectively.