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Atmospheric retrievals of emission spectra in the JWST era

Presentation #102.393 in the session Poster Session.

Published onJun 20, 2022
Atmospheric retrievals of emission spectra in the JWST era

Retrieval techniques are used to extract the optimal values of atmospheric parameters. With the launch of the James Webb Space Telescope (JWST), it is important to understand how these techniques can be appropriately used to obtain accurate and precise results. In this talk I focus on two assumptions commonly used in retrieval frameworks that could produce bias results in current and JWST quality data. The first is to assume that if there are clouds in emission that they are grey in nature. The second is to assume that the photospheric radius is constant with wavelength. In the first part of the talk I will focus on a reanalysis of the secondary eclipse measurements of HD 209458b and WASP-43b, taking into account that there may be scattering clouds. I find that there is no evidence for clouds in HD 209458b, a result that is consistent with the literature. However, I find that there is some evidence for scattering clouds in WASP-43b, the current data quality is not good enough to rule this out. In the second part of my talk I will focus on the impact that the variable photospheric radius has on extracting the molecular abundances from eclipse spectra. I find that, if retrieving assuming that the radius is constant with wavelength, bias results are obtained over the complete JWST wavelength range (NIRSpec PRISM + MIRI LRS) and the MIRI LRS wavelength region for typical hot Jupiters. Observing with the NIRSpec PRISM wavelength region alone does not result in biases in typical hot Jupiters, however it does for low gravity planets. No biases are found for high gravity planets. It is important these results are taken into account as JWST will observe an unprecedented amount of emission spectra of exoplanets.

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