James Webb Space Telescope Feed Post

Arxiv: Toward Robust Corrections for Stellar Contamination in JWST Exoplanet Transmission Spectra Published: 3/27/2023 8:40:53 PM Updated: 7/22/2024 9:00:20 PM

Paper abstract: Transmission spectroscopy is still the preferred characterization techniquefor exoplanet atmospheres, although it presents unique challenges thattranslate into characterization bottlenecks when robust mitigation strategiesare missing. Stellar contamination is one such challenge that can overpower theplanetary signal by up to an order of magnitude, and thus not accounting for itcan lead to significant biases in the derived atmospheric properties. Yet thisaccounting may not be straightforward, as important discrepancies exist betweenstate-of-the-art stellar models and measured spectra and between modelsthemselves. Here we explore the extent to which stellar models can be used toreliably correct for stellar contamination and yield a planet's uncontaminatedtransmission spectrum. We find that discrepancies between stellar models cansignificantly contribute to the noise budget of JWST transmission spectra ofplanets around stars with heterogeneous photospheres, the true number of uniquephotospheric spectral components and their properties can only be accuratelyretrieved when the stellar models have sufficient fidelity, and under suchoptimistic circumstances the contribution of stellar contamination to the noisebudget of a transmission spectrum is considerably below that of the photonnoise for the standard transit observation setup. Therefore, we advocate forfurther development of model spectra of stars and their active regions in adata-driven manner, empirical approaches for deriving spectra of photosphericcomponents using the observatories with which the atmospheric explorations arecarried out, and analysis techniques accounting for multimodal posteriordistributions for photospheric parameters of interest, which will beincreasingly revealed by precise JWST measurements.