squishyplanet: Modeling Transits of Non-spherical Exoplanets in JAX

TL;DR

squishyplanet is a Python package that models transits and phase curves of non-spherical exoplanets, enabling detailed analysis of their shapes and interior structures using upcoming high-precision observations.

Contribution

it extends existing transit models to account for non-spherical, triaxial exoplanets, facilitating more accurate interpretation of observational data.

Findings

implements a JAX-based model for non-spherical planets

enables analysis of phase curves and transit deviations

supports upcoming high-precision observational data

Abstract

While astronomers often assume that exoplanets are perfect spheres when analyzing observations, the subset of these distant worlds that are subject to strong tidal forces and/or rapid rotations are expected to be distinctly ellipsoidal or even triaxial. Since a planet's response to these forces is determined in part by its interior structure, measurements of an exoplanet's deviations from spherical symmetry can lead to powerful insights into its composition and surrounding environment. These shape deformations will imprint themselves on a planet's phase curve and transit lightcurve and cause small (1s-100s of parts per million) deviations from their spherical-planet counterparts. Until recently, these deviations were undetectable in typical real-world datasets due to limitations in photometric precision. Now, however, current and soon-to-come-online facilities such as JWST will routinely deliver observations that warrant the consideration of more complex models. To this end we present squishyplanet, a JAX-based Python package that implements an extension of the polynomial limb-darkened transit model presented in Agol et al. 2020 to non-spherical (triaxial) planets, as well as routines for modeling reflection and emission phase curves.