Catwoman: A transit modelling Python package for asymmetric light curves

TL;DR

Catwoman is a Python package designed to model asymmetric exoplanet transit light curves, accounting for potential differences in the planet's terminator regions, thus enabling more accurate characterization of exoplanets.

Contribution

It introduces a novel Python tool that extends existing transit models to include asymmetries caused by planetary terminator variations.

Findings

Allows modeling of asymmetric transit light curves

Supports any radially symmetric limb darkening law

Builds upon and extends the batman library

Abstract

When exoplanets pass in front of their stars, they imprint a transit signature on the stellar light curve which to date has been assumed to be symmetric in time, owing to the planet being modelled as a circular area occulting the stellar surface. However, this signature might be asymmetric due to different temperature/pressure and/or chemical compositions in the different terminator regions of the transiting planet. catwoman is a Python package that allows to model these asymmetric transit lightcurves, calculating lightcurves for any radially symmetric stellar limb darkening law, and where planets are modelled as two semi-circles, of different radii, using the integration algorithm developed in arXiv:1507.08285 and implemented in the batman library, from which catwoman builds upon.