New Mass and Radius Constraints on the LHS 1140 Planets -- LHS 1140 b is Either a Temperate Mini-Neptune or a Water World - Sorbonne Université Access content directly
Preprints, Working Papers, ... (Preprint) Year : 2023

New Mass and Radius Constraints on the LHS 1140 Planets -- LHS 1140 b is Either a Temperate Mini-Neptune or a Water World

Charles Cadieux
  • Function : Author
Mykhaylo Plotnykov
  • Function : Author
René Doyon
  • Function : Author
Diana Valencia
  • Function : Author
Farbod Jahandar
  • Function : Author
Lisa Dang
  • Function : Author
Thomas Fauchez
  • Function : Author
Ryan Cloutier
  • Function : Author
Collin Cherubim
  • Function : Author
Étienne Artigau
  • Function : Author
Neil Cook
  • Function : Author
Billy Edwards
  • Function : Author
Tim Hallatt
  • Function : Author
François Bouchy
  • Function : Author
Romain Allart
  • Function : Author
Lucile Mignon
  • Function : Author
Frédérique Baron
  • Function : Author
Susana Barros
  • Function : Author
Björn Benneke
  • Function : Author
B. Martins
  • Function : Author
Benjamin Charnay
  • Function : Author
Nicolas Cowan
  • Function : Author
J. de Medeiros
  • Function : Author
Xavier Delfosse
  • Function : Author
Elisa Delgado-Mena
  • Function : Author
Xavier Dumusque
  • Function : Author
David Ehrenreich
  • Function : Author
Nathan Hara
  • Function : Author
David Lafrenière
  • Function : Author
Yolanda Frensch
  • Function : Author
J. Hernández
  • Function : Author
Gaspare Lo Curto
  • Function : Author
Lison Malo
  • Function : Author
Claudio Melo
  • Function : Author
Dany Mounzer
  • Function : Author
Vera Maria Passeger
  • Function : Author
Francesco Pepe
  • Function : Author
Anne-Sophie Poulin-Girard
  • Function : Author
Nuno Santos
  • Function : Author
Danuta Sosnowska
  • Function : Author
Alejandro Suárez Mascareño
  • Function : Author
Simon Thibault
  • Function : Author
Valentina Vaulato
  • Function : Author
Gregg Wade
  • Function : Author
François Wildi
  • Function : Author

Abstract

LHS 1140 b and c are two small temperate exoplanets transiting a nearby M4.5 dwarf. The planetary system was observed with multiple facilities since its discovery in 2017, including MEarth, $Spitzer$, HARPS, ESPRESSO, HST, and TESS, placing strong constraints on the physical parameters of the planets and star. Here, we reanalyse the publicly available 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. This analysis reduces radial velocity uncertainties by 60% compared with published values derived from the cross-correlation function method. This improvement, combined with updated stellar parameters, consolidates our knowledge on the mass of LHS 1140 b (5.60$\pm$0.19 M$_{\oplus}$) and LHS 1140 c (1.91$\pm$0.06 M$_{\oplus}$) with unprecedented precision (3%). A joint analysis of transit data obtained with $Spitzer$, HST, and TESS allows us to refine the planetary radius for b (1.730$\pm$0.025 R$_{\oplus}$) and c (1.272$\pm$0.026 R$_{\oplus}$). 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 habitable zone planet is unlikely to be a rocky super-Earth, but rather a mini-Neptune with a $\sim$0.1% H/He-rich mass envelope or a water world with a water-mass fraction between 9 and 19% depending on the atmospheric composition and relative abundance of Fe and Mg. Although LHS 1140 c remains consistent with a rocky planet, we detect a 4$σ$ discrepancy in the transit depths measured by $Spitzer$ and TESS. Finally, we find no evidence of the candidate LHS 1140 d and attribute this 80-day signal to stellar activity.

Dates and versions

hal-04263311 , version 1 (28-10-2023)

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Cite

Charles Cadieux, Mykhaylo Plotnykov, René Doyon, Diana Valencia, Farbod Jahandar, et al.. New Mass and Radius Constraints on the LHS 1140 Planets -- LHS 1140 b is Either a Temperate Mini-Neptune or a Water World. 2023. ⟨hal-04263311⟩
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