Retrievals on NIRCam transmission and emission spectra of HD 189733b with PLATON 6, a GPU code for the JWST era
Michael Zhang, Kimberly Paragas, Jacob L. Bean, Joseph Yeung, Yayaati, Chachan, Thomas P. Greene, Jonathan Lunine, Drake Deming

TL;DR
This paper presents JWST/NIRCam spectra of HD 189733b analyzed with an upgraded GPU-accelerated version of PLATON, revealing atmospheric composition, methane depletion, and possible thermal inversion, advancing exoplanet atmospheric retrieval methods.
Contribution
Introduction of PLATON 6, a GPU-accelerated retrieval code supporting advanced features and improved speed, applied to analyze JWST spectra of HD 189733b.
Findings
Detection of H2O, CO2, CO, and H2S in spectra
Evidence of methane depletion on the terminator
Tentative thermal inversion at millibar pressures
Abstract
We present the 2.4--5.0 \um JWST/NIRCam emission spectrum of HD 189733b, along with an independent re-reduction of the previously published transmission spectrum at the same wavelengths. We use an upgraded version of PLanetary Atmospheric Tool for Observer Noobs (PLATON) to retrieve atmospheric parameters from both geometries. In transit, we obtain [M/H]= and C/O=, assuming a power-law haze and equilibrium chemistry with methane depletion. In eclipse, we obtain [M/H]= and C/O=, assuming a clear atmosphere and equilibrium chemistry without methane depletion. These results are consistent with each other, and with a re-run of our previously published joint retrieval of HST and Spitzer transmission and emission spectra. Accounting for methane depletion decreases the C/O ratio by 0.14/0.04…
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Taxonomy
TopicsOptical Systems and Laser Technology · Laser Design and Applications · Astronomical Observations and Instrumentation
