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Consistently Simulating a Wide Range of Atmospheric Scenarios for K2-18b with a Flexible Radiative Transfer Module

Scheucher, M. and Wunderlich, F. and Grenfell, John Lee and Godolt, Mareike and Schreier, Franz and Kappel, David and Haus, R and Herbst, K and Rauer, H (2020) Consistently Simulating a Wide Range of Atmospheric Scenarios for K2-18b with a Flexible Radiative Transfer Module. Astrophysical Journal, 898 (44), pp. 1-19. Institute of Physics (IOP) Publishing. doi: 10.3847/1538-4357/ab9084. ISSN 0004-637X.

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Official URL: https://iopscience.iop.org/article/10.3847/1538-4357/ab9084

Abstract

The atmospheres of small, potentially rocky exoplanets are expected to cover a diverse range in composition and mass. Studying such objects therefore requires flexible and wide-ranging modeling capabilities. We present in this work the essential development steps that lead to our flexible radiative transfer module, REDFOX, and validate REDFOX for the solar system planets Earth, Venus, and Mars, as well as for steam atmospheres. REDFOX is a k-distribution model using the correlated-k approach with the random overlap method for the calculation of opacities used in the δ-two-stream approximation for radiative transfer. Opacity contributions from Rayleigh scattering, UV/visible cross sections, and continua can be added selectively. With the improved capabilities of our new model, we calculate various atmospheric scenarios for K2-18b, a super-Earth/sub-Neptune with ~8 M ⊕ orbiting in the temperate zone around an M star, with recently observed H2O spectral features in the infrared. We model Earth-like, Venus-like, and H2–He primary atmospheres of different solar metallicity and show resulting climates and spectral characteristics compared to observed data. Our results suggest that K2-18b has an H2–He atmosphere with limited amounts of H2O and CH4. Results do not support the possibility of K2-18b having a water reservoir directly exposed to the atmosphere, which would reduce atmospheric scale heights, and with it the amplitudes of spectral features, making the latter inconsistent with the observations. We also performed tests for H2–He atmospheres up to 50 times solar metallicity, all compatible with the observations.

Item URL in elib:https://elib.dlr.de/137306/
Document Type:Article
Title:Consistently Simulating a Wide Range of Atmospheric Scenarios for K2-18b with a Flexible Radiative Transfer Module
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Scheucher, M.markus.scheucher (at) dlr.deUNSPECIFIED
Wunderlich, F.ZAA, Berlin Inst. Tech. (TUB), GermanyUNSPECIFIED
Grenfell, John LeeLee.Grenfell (at) dlr.deUNSPECIFIED
Godolt, MareikeMareike.Godolt (at) dlr.deUNSPECIFIED
Schreier, FranzFranz.Schreier (at) dlr.dehttps://orcid.org/0000-0001-7196-6599
Kappel, DavidDavid.Kappel (at) dlr.deUNSPECIFIED
Haus, RUni. PotsdamUNSPECIFIED
Herbst, KInstitut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, Kiel, GermanyUNSPECIFIED
Rauer, Hheike.rauer (at) dlr.deUNSPECIFIED
Date:20 July 2020
Journal or Publication Title:Astrophysical Journal
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:898
DOI :10.3847/1538-4357/ab9084
Page Range:pp. 1-19
Publisher:Institute of Physics (IOP) Publishing
ISSN:0004-637X
Status:Published
Keywords:Radiative transfer; computational methods; exoplanets; atmospheres
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Space Exploration
DLR - Research theme (Project):R - Vorhaben Planetary Evolution and Life (old)
Location: Berlin-Adlershof , Oberpfaffenhofen
Institutes and Institutions:Institute of Planetary Research > Extrasolar Planets and Atmospheres
Institute of Planetary Research > Leitungsbereich PF
Remote Sensing Technology Institute > Atmospheric Processors
Deposited By: Grenfell, John Lee
Deposited On:09 Nov 2020 15:22
Last Modified:10 Nov 2020 16:03

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