2025RNAAS...9..118T

Query : 2025RNAAS...9..118T

2025RNAAS...9..118T - Research Notes of the AAS, 9, 118 (2025/May-0)

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

TAYLOR J.

Abstract (from CDS):

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 ${\chi }_{\nu }^{2}$ 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 ${\chi }_{\nu }^{2}$ of 0.99. With only ∼2σ in favour of Gaussian features, I conclude no strong statistical evidence for spectral features.

Abstract Copyright: © 2025. The Author(s). Published by the American Astronomical Society.

Journal keyword(s): Exoplanet atmospheres - Exoplanet astronomy

Simbad objects: 1

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Number of rows : 1
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 K2-18b Pl 11 30 14.5177445592 +07 35 18.255348492           ~ 303 0

Query : 2025RNAAS...9..118T

Basic data :
K2-18b -- Extra-solar Planet
Other object types: otypes_help 		Pl? (2015ApJ,EPIC), Pl (2016ApJS,K2)
ICRS coord. (ep=J2000) : 		11 30 14.5177445592 +07 35 18.255348492 (Optical) [ 0.0220 0.0200 90 ] A 2020yCat.1350....0G
FK4 coord. (ep=B1950 eq=1950) : 		11 27 39.8122332755 +07 51 57.901559261 [ 0.0220 0.0200 90 ]
Gal coord. (ep=J2000) : 		254.6323771401059 +62.5757486784381 [ 0.0220 0.0200 90 ]
Proper motions mas/yr : 		-80.479 -133.007 [0.026 0.023 90] A 2020yCat.1350....0G
Parallaxes (mas): 		26.2469 [0.0266] A 2020yCat.1350....0G
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Identifiers (3) :
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EPIC 201912552.01 EPIC 201912552 b K2-18b

References (303 between 1850 and 2026) (Total 303)
Simbad bibliographic survey began in 1850 for stars (at least bright stars) and in 1983 for all other objects (outside the solar system).
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