A Benchmark JWST Near-Infrared Spectrum for the Exoplanet WASP-39b

TL;DR

This paper presents a comprehensive analysis of JWST transmission spectra for exoplanet WASP-39b across 0.5-5.2 microns, revealing atmospheric composition and improving spectral consistency using a uniform analysis approach.

Contribution

It introduces a uniform analysis method for JWST transmission spectra across multiple modes, enhancing atmospheric characterization accuracy for exoplanets.

Findings

Confirmed presence of multiple atmospheric molecules including Na, K, H2O, CO, CO2, SO2.

Achieved sub-percent precision in orbital and stellar parameters, matching asteroseismology.

Identified partial saturation issues in NIRSpec PRISM mode affecting data quality.

Abstract

Observing exoplanets through transmission spectroscopy supplies detailed information on their atmospheric composition, physics, and chemistry. Prior to JWST, these observations were limited to a narrow wavelength range across the near-ultraviolet to near-infrared, alongside broadband photometry at longer wavelengths. To understand more complex properties of exoplanet atmospheres, improved wavelength coverage and resolution are necessary to robustly quantify the influence of a broader range of absorbing molecular species. Here we present a combined analysis of JWST transmission spectroscopy across four different instrumental modes spanning 0.5-5.2 micron using Early Release Science observations of the Saturn-mass exoplanet WASP-39b. Our uniform analysis constrains the orbital and stellar parameters within sub-percent precision, including matching the precision obtained by the most precise asteroseismology measurements of stellar density to-date, and further confirms the presence of Na, K, H$_2$O, CO, CO$_2$, and SO$_2$ atmospheric absorbers. Through this process, we also improve the agreement between the transmission spectra of all modes, except for the NIRSpec PRISM, which is affected by partial saturation of the detector. This work provides strong evidence that uniform light curve analysis is an important aspect to ensuring reliability when comparing the high-precision transmission spectra provided by JWST.