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Arxiv: TransitFit: combined multi-instrument exoplanet transit fitting for JWST, HST and ground-based transmission spectroscopy studies Published: 3/22/2021 9:14:07 PM Updated: 10/30/2023 7:53:09 PM

Paper abstract: We present TransitFit, a package designed to fit exoplanetary transitlight-curves. TransitFit offers multi-epoch, multi-wavelength fitting ofmulti-telescope transit data. TransitFit allows per-telescope detrending to beperformed simultaneously with transit parameter fitting, including customdetrending. Host limb darkening can be fitted using prior conditioning fromstellar atmosphere models. We demonstrate TransitFit in a number of contexts.We model multi-telescope broadband optical data from the ground-based SPEARNETsurvey of the low-density hot-Neptune WASP-127b and compare results to apreviously published higher spectral resolution GTC/OSIRIS transmissionspectrum. Using TransitFit, we fit 26 transit epochs by TESS to recoverimproved ephemeris of the hot-Jupiter WASP-91b and a transit depth determinedto a precision of 111 ppm. We use TransitFit to conduct an investigation intothe contested presence of TTV signatures in WASP-126b using 180 transitsobserved by TESS, concluding that there is no statistically significantevidence for such signatures from observations spanning 27 TESS sectors. We fitHST observations of WASP-43b, demonstrating how TransitFit can use customdetrending algorithms to remove complex baseline systematics. Lastly, wepresent a transmission spectrum of the atmosphere of WASP-96b constructed fromsimultaneous fitting of JWST NIRISS Early Release Observations and archive HSTWFC3 transit data. The transmission spectrum shows generally goodcorrespondence between spectral features present in both datasets, despite verydifferent detrending requirements.