Fast Transit Computation Using Tabulated Stellar Intensities

TL;DR

This paper introduces a rapid method for calculating stellar light curves and related effects using tabulated stellar intensities, aiming to replace traditional limb darkening laws with more accurate, model-based intensities.

Contribution

The authors develop a fast computational technique that utilizes tabulated stellar intensities, reducing the expense of integrating over stellar surfaces for transit modeling.

Findings

Significantly speeds up transit and Rossiter-McLaughlin effect calculations.

Enables more accurate modeling using fundamental stellar parameters.

Reduces reliance on simplified limb darkening laws.

Abstract

Limb darkening laws are convenient parameterizations of the stellar intensity center-to-limb variation, and their use is ubiquitous in eclipse and transit modeling. But they are not "laws" in any sense -- they are simple approximations of the real intensity variations, and their limitations are becoming more and more apparent as stellar atmosphere models improve and higher precision data become available. When fitting eclipses and transit light curves, one would ideally like to use model intensities that are based on fundamental stellar parameters such as the mass, radius, and effective temperature of the star, rather than a limb darkening law representation and its coefficients. This is especially true when attempting to detect higher-order effects such as planetary oblateness, rings, satellites, or atmospheres. However, using model intensities requires numerically integrating many small-area "tiles" on the model stellar surface(s) and this has traditionally been too computationally expensive for general use. Here we present a fast technique to compute light curves and the Rossiter-McLaughlin effect that uses tabulated stellar models intensities. This is a step in the development of tools that obviate the need for limb darkening laws.