A super-Earth and a sub-Neptune orbiting the bright, quiet M3 dwarf TOI-1266

¹ Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland
e-mail: brice.demory@csh.unibe.ch
² Space Sciences, Technologies and Astrophysics Research (STAR) Institute, Université de Liège, Allée du 6 Août 19C, 4000 Liège, Belgium
³ Astrobiology Research Unit, Université de Liège, Allée du 6 Août 19C, 4000 Liège, Belgium
⁴ Instituto de Astronomía, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México 04510, México
⁵ Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 877, 22800 Ensenada, B.C., México
⁶ Universidad Nacional de Córdoba - Observatorio Astronómico de Córdoba, Laprida 854, X5000BGR, Córdoba, Argentina
⁷ Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
⁸ Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁹ Centre for Exoplanets and Habitability, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
¹⁰ Oukaimeden Observatory, High Energy Physics and Astrophysics Laboratory, Cadi Ayyad University, Marrakech, Morocco
¹¹ Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
¹² Observatoire astronomique de l’Université de Genève, 51 chemin des Maillettes, 1290 Versoix, Switzerland
¹³ Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
¹⁴ Instituto de Astrofísica de Canarias, Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
¹⁵ Department of Astronomy, 501 Campbell Hall, University of California at Berkeley, Berkeley, CA 94720, USA
¹⁶ Observatori Astronòmic Albanyà, Camí de Bassegoda s/n, Albanyà 17733, Girona, Spain
¹⁷ Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521, USA
¹⁸ Centro de Astrobiología (CAB, CSIC-INTA), Dpto. de Astrofísica, ESAC campus 28692 Villanueva de la Cañada (Madrid), Spain
¹⁹ Physikalisches Institut, University of Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland
²⁰ Cavendish Laboratory, J.J. Thomson Avenue, Cambridge, CB3 0HE, UK
²¹ Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
²² Department of Physics, University of California, Berkeley, Berkeley, CA
²³ Kotizarovci Observatory, Sarsoni 90, 51216 Viskovo, Croatia
²⁴ Department of Physics & Astronomy, Vanderbilt University, 6301 Stevenson Center Lane, Nashville, TN 37235, USA
²⁵ School of Physics & Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
²⁶ Società Astronomica Lunae, Castelnuovo Magra, Via Montefrancio 77, Italy
²⁷ Department of Aeronautics and Astronautics, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
²⁸ Department of Astrophysical Sciences, Princeton University, NJ 08544, USA
²⁹ NASA Ames Research Center, Moffett Field, CA, 94035, USA
³⁰ Departamento de Física Teórica y del Cosmos, Universidad de Granada, Campus de Fuentenueva s/n, 18071 Granada, Spain
³¹ Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
³² Department of A&A, University of California, Santa Cruz, CA 95064, USA
³³ Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
³⁴ Division of Geological and Planetary Sciences, California Institute of Technology, 1200 East California Blvd, Pasadena, CA 91125, USA
³⁵ Centre for Astrophysics, University of Southern Queensland, Toowoomba, QLD, Australia
³⁶ Department of Physics & Astronomy, University of California Irvine, Irvine, CA 92697, USA
³⁷ SETI Institute, Mountain View, CA 94043, USA
³⁸ Department of Astronomy, The University of Texas at Austin, Austin, TX 78712, USA

Received: 9 June 2020
Accepted: 20 July 2020

Abstract

We report the discovery and characterisation of a super-Earth and a sub-Neptune transiting the bright (K = 8.8), quiet, and nearby (37 pc) M3V dwarf TOI-1266. We validate the planetary nature of TOI-1266 b and c using four sectors of TESS photometry and data from the newly-commissioned 1-m SAINT-EX telescope located in San Pedro Mártir (México). We also include additional ground-based follow-up photometry as well as high-resolution spectroscopy and high-angular imaging observations. The inner, larger planet has a radius of R = 2.37_−0.12^+0.16 R_⊕ and an orbital period of 10.9 days. The outer, smaller planet has a radius of R = 1.56_−0.13^+0.15 R_⊕ on an 18.8-day orbit. The data are found to be consistent with circular, co-planar and stable orbits that are weakly influenced by the 2:1 mean motion resonance. Our TTV analysis of the combined dataset enables model-independent constraints on the masses and eccentricities of the planets. We find planetary masses of M_p = 13.5_−9.0^+11.0 M_⊕ (<36.8 M_⊕ at 2-σ) for TOI-1266 b and 2.2_−1.5^+2.0 M_⊕ (<5.7 M_⊕ at 2-σ) for TOI-1266 c. We find small but non-zero orbital eccentricities of 0.09_−0.05^+0.06 (<0.21 at 2-σ) for TOI-1266 b and 0.04 ± 0.03 (< 0.10 at 2-σ) for TOI-1266 c. The equilibrium temperatures of both planets are of 413 ± 20 and 344 ± 16 K, respectively, assuming a null Bond albedo and uniform heat redistribution from the day-side to the night-side hemisphere. The host brightness and negligible activity combined with the planetary system architecture and favourable planet-to-star radii ratios makes TOI-1266 an exquisite system for a detailed characterisation.