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Arxiv: A Benchmark JWST Near-Infrared Spectrum for the Exoplanet WASP-39b Published: 7/18/2024 11:43:36 PM Updated: 7/18/2024 11:43:36 PM

Paper abstract: Observing exoplanets through transmission spectroscopy supplies detailedinformation on their atmospheric composition, physics, and chemistry. Prior toJWST, these observations were limited to a narrow wavelength range across thenear-ultraviolet to near-infrared, alongside broadband photometry at longerwavelengths. To understand more complex properties of exoplanet atmospheres,improved wavelength coverage and resolution are necessary to robustly quantifythe influence of a broader range of absorbing molecular species. Here wepresent a combined analysis of JWST transmission spectroscopy across fourdifferent instrumental modes spanning 0.5-5.2 micron using Early ReleaseScience observations of the Saturn-mass exoplanet WASP-39b. Our uniformanalysis constrains the orbital and stellar parameters within sub-percentprecision, including matching the precision obtained by the most preciseasteroseismology measurements of stellar density to-date, and further confirmsthe presence of Na, K, H_2O, CO, CO_2, and SO_2 atmospheric absorbers.Through this process, we also improve the agreement between the transmissionspectra of all modes, except for the NIRSpec PRISM, which is affected bypartial saturation of the detector. This work provides strong evidence thatuniform light curve analysis is an important aspect to ensuring reliabilitywhen comparing the high-precision transmission spectra provided by JWST.