A Second Planet with an Earth-like Composition Orbiting The Nearby M dwarf LHS 1140


LHS 1140

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 HARPS, 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 of the mass and radius of LHS 1140 b to be 6.98 ± 0.98 M⊕ and 1.727 ± 0.032 R⊕.

The mean densities of planets b and c are 7.5 ± 1.0 g/cm3 and 4.7 ± 1.1 g/cm3, 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 co-planar 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.

Kristo Ment (1), Jason A. Dittmann (2), Nicola Astudillo-Defru (3), David Charbonneau (1), Jonathan Irwin (1), Xavier Bonfils (4), Felipe Murgas (5), Jose-Manuel Almenara (4), Thierry Forveille (4), Eric Agol (6), Sarah Ballard (7), Zachory K. Berta-Thompson (8), François Bouchy (9), Ryan Cloutier (10, 11 and 12), Xavier Delfosse (4), René Doyon (12), Courtney D. Dressing (13), Gilbert A. Esquerdo (1), Raphaëlle D. Haywood (1), David M. Kipping (14), David W. Latham (1), Christophe Lovis (9), Elisabeth R. Newton (7), Francesco Pepe (9), Joseph E. Rodriguez (1), Nuno C. Santos (15 and 16), Thiam-Guan Tan (17), Stephane Udry (9), Jennifer G. Winters (1), Anaël Wünsche (4) ((1) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA, (2) 51 Pegasi b Postdoctoral Fellow, Massachusetts Institute of Technology, Cambridge, MA, USA, (3) Departamento de Astronomía, Universidad de Concepción, Concepción, Chile, (4) Université Grenoble Alpes, CNRS, IPAG, Grenoble, France, (5) Instituto de Astrofísica de Canarias (IAC), Tenerife, Spain, (6) Astronomy Department, University of Washington, Seattle, WA, USA, (7) Massachusetts Institute of Technology, Cambridge, MA, USA, (8) Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO, USA, (9) Observatoire de l'Université de Genève, Versoix, Switzerland, (10) Dept. of Astronomy & Astrophysics, University of Toronto, Toronto, ON, Canada, (11) Centre for Planetary Sciences, Dept. of Physical & Environmental Sciences, University of Toronto Scarborough, Toronto, ON, Canada, (12) Institut de Recherche sur les Exoplanètes, Département de physique, Université de Montréal, Montréal, QC, Canada, (13) Department of Astronomy, University of California, Berkeley, CA, USA, (14) Department of Astronomy, Columbia University, New York, NY, USA, (15) Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Porto, Portugal, (16) Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Porto, Portugal, (17) Perth Exoplanet Survey Telescope, Perth, Australia)

(Submitted on 1 Aug 2018)

Comments: 21 pages, 8 figures, submitted to AAS journals
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1808.00485 [astro-ph.EP] (or arXiv:1808.00485v1 [astro-ph.EP] for this version)
Submission history
From: Kristo Ment
[v1] Wed, 1 Aug 2018 18:03:01 GMT (2171kb,D)

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