2021A&A...656A..90K


Query : 2021A&A...656A..90K

2021A&A...656A..90K - Astronomy and Astrophysics, volume 656A, 90-90 (2021/12-1)

Implementation of disequilibrium chemistry to spectral retrieval code ARCiS and application to 16 exoplanet transmission spectra. Indication of disequilibrium chemistry for HD 209458b and WASP-39b.

KAWASHIMA Y. and MIN M.

Abstract (from CDS):


Context. The retrieval approach is currently a standard method for deriving atmospheric properties from observed spectra of exoplanets. However, the approach ignores disequilibrium chemistry in most current retrieval codes, which can lead to a misinterpretation of the metallicity or elemental abundance ratios of the atmosphere.
Aims. We have implemented the disequilibrium effect of vertical mixing or quenching for the major species in hydrogen and helium-dominated atmospheres, namely CH4, CO, H2O, NH3, N2, and CO2, for the spectral retrieval code ARCiS with a physical basis.
Methods. We used the chemical relaxation method and developed a module to compute the profiles of molecular abundances, taking the disequilibrium effect into account. Then, using ARCiS updated with this module, we performed retrievals of the observed transmission spectra of 16 exoplanets with sizes ranging from that of Jupiter to mini-Neptunes.
Results. We find indications of disequilibrium chemistry for HD 209458b (≥4.1σ) and WASP-39b (≥2.7σ). The retrieved spectrum of HD 209458b exhibits a strong NH3 absorption feature at 10.5 µm that is accessible by JWST owing to an enhanced abundance of NH3 due to the quenching effect. This feature is absent in the spectrum retrieved assuming equilibrium chemistry, which makes HD 209458b an ideal target for studying disequilibrium chemistry in exoplanet atmospheres. Moreover, for HAT-P-11b and GJ 436b, we obtain relatively different results compared to the retrieval with the equilibrium assumption, such as a 2.9σ difference for the C/O ratio. We have also examined the retrieved eddy diffusion coefficient but could not identify a trend over the equilibrium temperature, possibly due to the limits of the current observational precision.
Conclusions. We have demonstrated that the assumption of equilibrium chemistry can lead to a misinterpretation of the observed data, showing that spectral retrieval with a consideration of disequilibrium chemistry is essential in the era of JWST and Ariel.

Abstract Copyright: © ESO 2021

Journal keyword(s): planets and satellites: gaseous planets - planets and satellites: atmospheres - planets and satellites: composition

Simbad objects: 16

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Number of rows : 16
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 WASP-12b Pl 06 30 32.7966788910 +29 40 20.266334158           G0 700 1
2 NAME LP 424-4b Pl 07 59 05.8395618539 +15 23 29.240025256           ~ 259 1
3 WASP-19b Pl 09 53 40.0764883458 -45 39 33.055979403           ~ 339 1
4 HD 97658b Pl 11 14 33.1613362847 +25 42 37.391912066           ~ 185 1
5 WASP-31b Pl 11 17 45.3578468391 -19 03 17.216528280           ~ 115 1
6 Ross 905b Pl 11 42 11.0933874353 +26 42 23.658083337           ~ 739 1
7 HAT-P-12b Pl 13 57 33.4668726399 +43 29 36.601508739           ~ 158 1
8 HAT-P-26b Pl 14 12 37.5331103311 +04 03 36.116569918           ~ 143 1
9 WASP-39b Pl 14 29 18.4151765921 -03 26 40.203046112           ~ 133 1
10 CD-27 10695b Pl 15 59 50.9489706053 -28 03 42.309432433           ~ 236 1
11 NAME G 139-21b Pl 17 15 18.9337265994 +04 57 50.064695682           ~ 653 1
12 BD+47 2936b Pl 19 50 50.2474562793 +48 04 51.097364378           ~ 375 1
13 HD 189733b Pl 20 00 43.7130382888 +22 42 39.071811263           ~ 1323 1
14 HD 209458b Pl 22 03 10.7729598762 +18 53 03.548248479           ~ 1742 1
15 NAME BD+37 4734Bb Pl 22 57 46.8443014981 +38 40 30.355384717           ~ 230 1
16 WASP-6b Pl 23 12 37.7368657624 -22 40 26.277489164           ~ 123 1

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2023.01.31-01:19:36

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