James Webb Space Telescope Feed Post

Arxiv: The role of cloud particle properties on WASP-39b transmission spectrum based on JWST/NIRSpec observations Published: 1/29/2025 6:11:33 PM Updated: 1/29/2025 6:11:33 PM

Paper abstract: Aerosols are capable of having a huge influence on reflected, emitted andtransmitted planetary spectra. The Near InfraRed Spectrograph (NIRSpec) usingthe PRISM mode on board of the James Webb Space Telescope (JWST) is providingvaluable data of transit spectra over a wide spectral range that is able tocover the whole contribution of aerosols, potentially disentangling them fromother constituents and thus allowing to constrain their properties. We aim toinvestigate whether NIRSpec/PRISM JWST transmission spectroscopy observations,in addition to being useful to detect and determine the abundance of gases moreaccurately than any previous instruments, are also capable of studying thephysical properties of the aerosols in exoplanetary atmospheres. We performnested sampling Bayesian retrievals with MultiNest library. We use thePlanetary Spectrum Generator (PSG) and the Modelled Optical Properties ofenSeMbles of Aerosol Particles (MOPSMAP) database as tools for the forwardsimulations and NIRSpec/PRISM JWST previously published observations ofWASP-39b as input data. Retrievals indicate that models including an aerosolextinction weakly increasing or sharply decreasing with wavelength aredecisively better than those with a flat transmission and that this increaseddegree of complexity is supported by the kind of data that JWST/NIRSpec canprovide. Given other physical constraints from previous works, the scenario ofweakly increasing particle extinction is favoured. We also find that this alsohas an effect on the retrieved gas abundances. JWST observations have thepotential to study some physical characteristics of exoplanetary clouds, inparticular their overall dependence of transmissivity with wavelength. In fact,it is important to implement more detailed aerosol models as their extinctionmay affect significantly retrieved molecular abundances.