Are There Spectral Features in the MIRI/LRS Transmission Spectrum of K2-18b?

Journal article

Determining the composition of an exoplanet atmosphere relies on the presence of detectable spectral features. The strongest spectral features, including dimethyl sulphide (DMS), look approximately Gaussian. Here, I perform a suite of Gaussian feature analyses to find any statistically significant spectral features in the recently published MIRI/LRS spectrum of K2-18b. In N. Madhusudhan et al., they claim a 3.4σ detection of spectral features compared to a flat line. In 5 out of 6 tests, I find the data preferred a flat line over a Gaussian model, with a χν2 of 1.06. When centering the Gaussian where the absorptions for DMS and DMDS peak, I find ln(B) = 1.21 in favour of the Gaussian model, with a χν2 of 0.99. With only ∼2σ in favour of Gaussian features, I conclude no strong statistical evidence for spectral features.

Authors: Taylor, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Astronomical Society
• Journal: Research Notes of the American Astronomical Society
• Volume: 9
• Issue: 5
• Article number: 118
• Publication date: 2025-05-16
• Acceptance date: 2025-05-14
• DOI: 10.3847/2515-5172/add881
• EISSN: 2515-5172
• Language: English
• Keywords: Exoplanet atmospheres; Exoplanet astronomy