A Second Terrestrial Planet Orbiting the Nearby M Dwarf LHS 1140

Kristo Ment , Jason A. Dittmann , Nicola Astudillo-Defru (1) , David Charbonneau , Jonathan Irwin (2) , Xavier Bonfils (3) , Felipe Murgas , Jose-Manuel Almenara (3) , Thierry Forveille (3) , Eric Agol (4) , Sarah Ballard , Zachory K. Berta-Thompson , François Bouchy (5) , Ryan Cloutier , Xavier Delfosse (3) , Rene Doyon (6) , Courtney D. Dressing , Gilbert A. Esquerdo , Raphaëlle D. Haywood , David M. Kipping , David W. Latham (2) , Christophe Lovis (7) , Elisabeth R. Newton , Francesco Pepe (7) , Joseph E. Rodriguez , Nuno C. Santos (7) , Thiam-Guan Tan , Stéphane Udry (7) , Jennifer G. Winters , Anaël Wünsche , Jason Dittmann , Zachory Berta-Thompson (8) , Courtney Dressing , Gilbert Esquerdo , Raphaëlle D. Haywood (9) , David Kipping , David Latham , Elisabeth Newton , Joseph Rodriguez , Nuno Santos (10) , Jennifer Winters

1 Universidad de Concepción - University of Concepcion [Chile]
2 CfA - Harvard-Smithsonian Center for Astrophysics
3 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
4 University of Washington [Seattle]
5 IAP - Institut d'Astrophysique de Paris
6 Departement de physique and Observatoire du Mont Megantic
7 ObsGE - Observatoire Astronomique de l'Université de Genève
8 Department of Astrophysical and Planetary Sciences [Boulder]
9 SUPA School of Physics and Astronomy [University of St Andrews]
10 CERN - European Organization for Nuclear Research

LHS 1140 is a nearby mid-M dwarf known to host a temperate rocky super-Earth (LHS 1140 b) on a 24.737-day orbit. Based on photometric observations by MEarth and Spitzer as well as Doppler spectroscopy from the High Accuracy Radial velocity Planet Searcher, we report the discovery of an additional transiting rocky companion (LHS 1140 c) with a mass of 1.81 ± 0.39 M ⊕ and a radius of 1.282 ± 0.024 R ⊕ on a tighter, 3.77795-day orbit. We also obtain more precise estimates for the mass and radius of LHS 1140 b, which are 6.98 ± 0.89 M ⊕ and 1.727 ± 0.032 R ⊕. The mean densities of planets b and c are 7.5 ± 1.0 g cm-3 and 4.7 ± 1.1 g cm-3, respectively, both consistent with the Earth’s ratio of iron to magnesium silicate. The orbital eccentricities of LHS 1140 b and c are consistent with circular orbits and constrained to be below 0.06 and 0.31, respectively, with 90% confidence. Because the orbits of the two planets are coplanar and because we know from previous analyses of Kepler data that compact systems of small planets orbiting M dwarfs are commonplace, a search for more transiting planets in the LHS 1140 system could be fruitful. LHS 1140 c is one of the few known nearby terrestrial planets whose atmosphere could be studied with the upcoming James Webb Space Telescope.

Mots clés: techniques: radial velocities; techniques: photometric; planets and satellites: terrestrial planets; planets and satellites: detection

Domaines: Planète et Univers [physics]; Astrophysique [astro-ph]

Kristo Ment, Jason A. Dittmann, Nicola Astudillo-Defru, David Charbonneau, Jonathan Irwin, et al.. A Second Terrestrial Planet Orbiting the Nearby M Dwarf LHS 1140. The Astronomical Journal, 2019, 157 (1), pp.32. ⟨10.3847/1538-3881/aaf1b1⟩. ⟨hal-02393102⟩