New Mass and Radius Constraints on the LHS 1140 Planets: LHS 1140 b Is either a Temperate Mini-Neptune or a Water World
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Published:2024-01-01
Issue:1
Volume:960
Page:L3
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ISSN:2041-8205
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Container-title:The Astrophysical Journal Letters
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language:
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Short-container-title:ApJL
Author:
Cadieux CharlesORCID, Plotnykov MykhayloORCID, Doyon RenéORCID, Valencia DianaORCID, Jahandar FarbodORCID, Dang LisaORCID, Turbet MartinORCID, Fauchez Thomas J.ORCID, Cloutier RyanORCID, Cherubim CollinORCID, Artigau ÉtienneORCID, Cook Neil J.ORCID, Edwards BillyORCID, Hallatt TimORCID, Charnay BenjaminORCID, Bouchy FrançoisORCID, Allart RomainORCID, Mignon LucileORCID, Baron FrédériqueORCID, Barros Susana C. C.ORCID, Benneke BjörnORCID, Canto Martins B. L.ORCID, Cowan Nicolas B.ORCID, De Medeiros J. R.ORCID, Delfosse XavierORCID, Delgado-Mena ElisaORCID, Dumusque XavierORCID, Ehrenreich DavidORCID, Frensch Yolanda G. C.ORCID, González Hernández J. I.ORCID, Hara Nathan C.ORCID, Lafrenière DavidORCID, Lo Curto GaspareORCID, Malo LisonORCID, Melo ClaudioORCID, Mounzer DanyORCID, Passeger Vera MariaORCID, Pepe FrancescoORCID, Poulin-Girard Anne-Sophie, Santos Nuno C.ORCID, Sosnowska Danuta, Suárez Mascareño AlejandroORCID, Thibault SimonORCID, Vaulato ValentinaORCID, Wade Gregg A.ORCID, Wildi FrançoisORCID
Abstract
Abstract
The two-planet transiting system LHS 1140 has been extensively observed since its discovery in 2017, notably with Spitzer, HST, TESS, and ESPRESSO, placing strong constraints on the parameters of the M4.5 host star and its small temperate exoplanets, LHS 1140 b and c. Here, we reanalyze the ESPRESSO observations of LHS 1140 with the novel line-by-line framework designed to fully exploit the radial velocity content of a stellar spectrum while being resilient to outlier measurements. The improved radial velocities, combined with updated stellar parameters, consolidate our knowledge of the mass of LHS 1140 b (5.60 ± 0.19 M
⊕) and LHS 1140 c (1.91 ± 0.06 M
⊕) with an unprecedented precision of 3%. Transits from Spitzer, HST, and TESS are jointly analyzed for the first time, allowing us to refine the planetary radii of b (1.730 ± 0.025 R
⊕) and c (1.272 ± 0.026 R
⊕). Stellar abundance measurements of refractory elements (Fe, Mg, and Si) obtained with NIRPS are used to constrain the internal structure of LHS 1140 b. This planet is unlikely to be a rocky super-Earth, as previously reported, but rather a mini-Neptune with a ∼0.1% H/He envelope by mass or a water world with a water-mass fraction between 9% and 19%, depending on the atmospheric composition and relative abundance of Fe and Mg. While the mini-Neptune case would not be habitable, a water-abundant LHS 1140 b potentially has habitable surface conditions according to 3D global climate models, suggesting liquid water at the substellar point for atmospheres with relatively low CO2 concentration, from Earth-like to a few bars.
Publisher
American Astronomical Society
Subject
Space and Planetary Science,Astronomy and Astrophysics
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