Stellar limb darkening. A new MPS-ATLAS library for Kepler, TESS, CHEOPS, and PLATO passbands

Abstract

Context. The detection of the first exoplanet paved the way into the era of transit photometry space missions with a revolutionary photometric precision that aim at discovering new exoplanetary systems around different types of stars. With this high precision, it is possible to derive very accurately the radii of exoplanets which is crucial for constraining their type and composition. However, it requires an accurate description of host stars, especially their center-to-limb variation of intensities (so called limb darkening) as it affects the planet-to-star radius ratio determination. Aims. We aim at improving the accuracy of limb darkening calculations for stars with a wide range of fundamental parameters. Methods. We used the recently developed 1D Merged Parallelised Simplified ATLAS (MPS-ATLAS) code to compute model atmosphere structures and to synthesize stellar limb darkening on a very fine grid of stellar parameters. For the computations we utilised the most accurate information on chemical element abundances and mixing length parameters including convective overshoot. The stellar limb darkening was fitted using the two most accurate limb darkening laws: the power-2 and 4-parameters non-linear laws.Results. We present a new extensive library of stellar model atmospheric structures, the synthesized stellar limb darkening curves, and the coefficients of parameterized limb-darkening laws on a very fine grid of stellar parameters in the Kepler, TESS, CHEOPS, and PLATO passbands. The fine grid allows overcoming the sizable errors introduced by the need to interpolate. Our computations of solar limb darkening are in a good agreement with available solar measurements at different view angles and wavelengths. Our computations of stellar limb darkening agree well with available measurements of Kepler stars. A new grid of stellar model structures, limb darkening and their fitted coefficients in different broad passbands is provided in online tables (CDS).

Can 1D radiative equilibrium models of faculae be used for calculating contamination of transmission spectra?

“…Subsequently we calculate the specific intensities for the same viewing-angles as used in the 3D approach. We note that the 1D calculations using the MPS-ATLAS code have been extensively validated against available observations and models of quiet solar/stellar atmospheres (see Witzke et al 2021;Kostogryz et al 2022). Moreover, we compare the 3D contrasts to the state-of-the-art practice in exoplanetary atmospheric retrievals, namely, contrasts derived from the PHOENIX spectral grid (Husser et al 2013).…”