A hot terrestrial planet orbiting the bright M dwarf L 168-9 unveiled by TESS ^{★,★★,★★★}

¹ Departamento de Matemática y Física Aplicadas, Universidad Católica de la Santísima Concepción, Alonso de Rivera 2850, Concepción, Chile
e-mail: nastudillo@ucsc.cl
² Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
³ Department of Astronomy & Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON, M5S 3H4, Canada
⁴ Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101, USA
⁵ Center of Astro-Engineering UC, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile
⁶ Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile
⁷ Millennium Institute of Astrophysics, Santiago, Chile
⁸ Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
⁹ Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
¹⁰ Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
¹¹ Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA
¹² NASA Ames Research Center, Moffett Field, CA 94035, USA
¹³ Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA
¹⁴ Dunlap Institute for Astronomy and Astrophysics, University of Toronto, Ontario M5S 3H4, Canada
¹⁵ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
¹⁶ Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
¹⁷ Institut de Recherche sur les Exoplanètes, Département de Physique, Université de Montréal, Montréal QC, H3C 3J7, Canada
¹⁸ Observatoire de Genève, Université de Genève, 51 ch. des Maillettes, 1290 Sauverny, Switzerland
¹⁹ Cerro Tololo Inter-American Observatory, Casilla 603, La Serena, Chile
²⁰ Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Road NW, Washington DC 20015, USA
²¹ American Association of Variable Star Observers, 49 Bay State Road, Cambridge, MA 02138, USA
²² Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
²³ Physics & Astronomy Department, University of Kansas, Lawrence, KS 66044, USA
²⁴ Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales. Buenos Aires, Argentina
²⁵ CONICET – Universidad de Buenos Aires, Instituto de Astronomía y Física del Espacio (IAFE), Buenos Aires, Argentina
²⁶ Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM, USA
²⁷ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
²⁸ European Southern Observatory, Alonso de Córdova 3107, Vitacura, Región Metropolitana, Chile
²⁹ Universidad de Concepción, Departamento de Astronomía, Casilla 160-C, Concepción, Chile
³⁰ Physics Department and Tsinghua Centre for Astrophysics, Tsinghua University, Beijing 100084, PR China
³¹ Centre for Astrophysics, University of Southern Queensland, Toowoomba, QLD 4350, Australia
³² Max-Planck-Institut fur Astronomie, Künigstuhl 17, 69117 Heidelberg, Germany
³³ Department of Physics, Southern Connecticut State University, 501 Crescent Street, New Haven, CT 06515, USA
³⁴ Campo Catino Astronomical Observatory, Regione Lazio, Guarcino (FR) 03010, Italy
³⁵ Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile
³⁶ Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Av. Diagonal las Torres 2640, Peñalolén, Santiago, Chile
³⁷ Department of Physics and Astronomy, University of Louisville, Louisville, KY 40292, USA
³⁸ Department of Physics and Astronomy, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255, USA
³⁹ Departamento de Física, Universidade Federal do Rio Grande do Norte, 59078-970 Natal, RN, Brazil
⁴⁰ Georgia State University, Department of Physics & Astronomy, 25 Park Place NE #605, USA
⁴¹ Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, PT4150-762 Porto, Portugal
⁴² Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Porto, Portugal
⁴³ SETI Institute, Moffett Field, CA 94035, USA
⁴⁴ Center for Space Research, MIT, 37-414, Cambridge, MA 02139, USA

Received: 22 November 2019
Accepted: 27 January 2020

Abstract

We report the detection of a transiting super-Earth-sized planet (R = 1.39 ± 0.09 R_⊕) in a 1.4-day orbit around L 168-9 (TOI-134), a bright M1V dwarf (V = 11, K = 7.1) located at 25.15 ± 0.02 pc. The host star was observed in the first sector of the Transiting Exoplanet Survey Satellite (TESS) mission. For confirmation and planet mass measurement purposes, this was followed up with ground-based photometry, seeing-limited and high-resolution imaging, and precise radial velocity (PRV) observations using the HARPS and Magellan/PFS spectrographs. By combining the TESS data and PRV observations, we find the mass of L 168-9 b to be 4.60 ± 0.56 M_⊕ and thus the bulk density to be 1.74_−0.33^+0.44 times higher than that of the Earth. The orbital eccentricity is smaller than 0.21 (95% confidence). This planet is a level one candidate for the TESS mission’s scientific objective of measuring the masses of 50 small planets, and it is one of the most observationally accessible terrestrial planets for future atmospheric characterization.