Debris Disks can Contaminate Mid-Infrared Exoplanet Spectra: Evidence for a Circumstellar Debris Disk around Exoplanet Host WASP-39

TL;DR

Circumstellar debris disks can significantly contaminate mid-infrared exoplanet spectra, as evidenced by the potential debris disk around WASP-39, affecting the interpretation of planetary atmospheres.

Contribution

This study provides evidence for a circumstellar debris disk around WASP-39 and demonstrates its impact on mid-infrared exoplanet transmission spectra, highlighting a source of astrophysical contamination.

Findings

Detection of an unexplained dip at ~10 μm in the spectrum.

Spectral energy distribution shows excess flux consistent with a debris disk.

Even faint debris disks can contaminate MIRI exoplanet spectra.

Abstract

The signal from a transiting planet can be diluted by astrophysical contamination. In the case of circumstellar debris disks, this contamination could start in the mid-infrared and vary as a function of wavelength, which would then change the observed transmission spectrum for any planet in the system. The MIRI/LRS WASP-39b transmission spectrum shows an unexplained dip starting at $\sim$10 $\mu$m that could be caused by astrophysical contamination. The spectral energy distribution displays excess flux at similar levels to that which are needed to create the dip in the transmission spectrum. In this article, we show that this dip is consistent with the presence of a bright circumstellar debris disk, at a distance of $>$2 au. We discuss how a circumstellar debris disk like that could affect the atmosphere of WASP-39b. We also show that even faint debris disks can be a source of contamination in MIRI exoplanet spectra.