Greening of the brown-dwarf desert EPIC 212036875b: a 51 M-J object in a 5-day orbit around an F7V star
Journal article, 2019
Context. Although more than 2000 brown dwarfs have been detected to date, mainly from direct imaging, their characterisation is difficult due to their faintness and model-dependent results. In the case of transiting brown dwarfs, however, it is possible to make direct high-precision observations. Aims. Our aim is to investigate the nature and formation of brown dwarfs by adding a new well-characterised object, in terms of its mass, radius and bulk density, to the currently small sample of less than 20 transiting brown dwarfs. Methods. One brown dwarf candidate was found by the KESPRINT consortium when searching for exoplanets in the K2 space mission Campaign 16 field. We combined the K2 photometric data with a series of multicolour photometric observations, imaging, and radial velocity measurements to rule out false positive scenarios and to determine the fundamental properties of the system. Results. We report the discovery and characterisation of a transiting brown dwarf in a 5.17-day eccentric orbit around the slightly evolved F7V star EPIC 212036875. We find a stellar mass of 1.15 +/- 0.08 M-circle dot, a stellar radius of 1.41 +/- 0.05 R-circle dot, and an age of 5.1 +/- 0.9 Gyr. The mass and radius of the companion brown dwarf are 51 +/- 2 M-J and 0.83 +/- 0.03 R-J, respectively, corresponding to a mean density of 108(-13)(+15) g cm(-3). Conclusions. EPIC 212036875 b is a rare object that resides in the brown-dwarf desert. In the mass-density diagram for planets, brown dwarfs, and stars, we find that all giant planets and brown dwarfs follow the same trend from similar to 0.3 M-J to the turn-over to hydrogen burning stars at similar to 73 M-J. EPIC 212036875 b falls close to the theoretical model for mature H/He dominated objects in this diagram as determined by interior structure models. We argue that EPIC 212036875 b formed via gravitational disc instabilities in the outer part of the disc, followed by a quick migration. Orbital tidal circularisation may have started early in its history for a brief period when the brown dwarf's radius was larger. The lack of spin-orbit synchronisation points to a weak stellar dissipation parameter (Q(star)' greater than or similar to 10(8)), which implies a circularisation timescale of greater than or similar to 23 Gyr, or suggests an interaction between the magnetic and tidal forces of the star and the brown dwarf.
stars: fundamental parameters
techniques: photometric
planetary systems
stars: individual: EPIC 212036875
techniques: radial velocities
Author
Carina Persson
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Szilard Csizmadia
German Aerospace Center (DLR)
Alexander J. Mustill
Lund University
Malcolm Fridlund
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Leiden University
Artie P. Hatzes
Thüringer Landessternwarte Tautenburg
Grzegorz Nowak
University of La Laguna
Instituto de Astrofísica de Canarias
Iskra Georgieva
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Davide Gandolfi
University of Turin
Melvyn B. Davies
Lund University
John H. Livingston
University of Tokyo
Enric Palle
University of La Laguna
Instituto de Astrofísica de Canarias
Pilar Montanes Rodriguez
Instituto de Astrofísica de Canarias
University of La Laguna
Michael Endl
The University of Texas at Austin
Teruyuki Hirano
Tokyo Institute of Technology
Jorge Prieto-Arranz
Instituto de Astrofísica de Canarias
University of La Laguna
Judith Korth
University of Cologne
Sascha Grziwa
University of Cologne
Massimiliano Esposito
Thüringer Landessternwarte Tautenburg
Simon Albrecht
Aarhus University
Marshall C. Johnson
Ohio State University
Oscar Barragan
University of Oxford
University of Turin
Hannu Parviainen
University of La Laguna
Instituto de Astrofísica de Canarias
Vincent Van Eylen
Princeton University
Roi Alonso Sobrino
Instituto de Astrofísica de Canarias
University of La Laguna
Paul G. Beck
University of La Laguna
University of Graz
Instituto de Astrofísica de Canarias
Juan Cabrera
German Aerospace Center (DLR)
Ilaria Carleo
Wesleyan University
William D. Cochran
The University of Texas at Austin
Fei Dai
Princeton University
Massachusetts Institute of Technology (MIT)
Hans J. Deeg
Instituto de Astrofísica de Canarias
University of La Laguna
Jerome P. de Leon
University of Tokyo
Philipp Eigmueller
German Aerospace Center (DLR)
Anders Erikson
German Aerospace Center (DLR)
Akai Fukui
National Institutes of Natural Sciences
Lucia Gonzalez-Cuesta
Instituto de Astrofísica de Canarias
University of La Laguna
Eike W. Guenther
Thüringer Landessternwarte Tautenburg
Diego Hidalgo
Instituto de Astrofísica de Canarias
University of La Laguna
Maria Hjorth
Aarhus University
Petr Kabath
Czech Academy of Sciences
Emil Knudstrup
Aarhus University
Nobuhiko Kusakabe
National Institutes of Natural Sciences
Kristine W. F. Lam
Technische Universität Berlin
Mikkel N. Lund
Aarhus University
Rafael Luque
University of La Laguna
Instituto de Astrofísica de Canarias
Savita Mathur
Instituto de Astrofísica de Canarias
University of La Laguna
Felipe Murgas
University of La Laguna
Instituto de Astrofísica de Canarias
Norio Narita
Instituto de Astrofísica de Canarias
University of Tokyo
Japan Science and Technology Agency
National Institutes of Natural Sciences
David Nespral
University of La Laguna
Instituto de Astrofísica de Canarias
Prajwal Niraula
Massachusetts Institute of Technology (MIT)
Henrik Olofsson
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Martin Paetzold
University of Cologne
Heike Rauer
German Aerospace Center (DLR)
Technische Universität Berlin
Seth Redfield
Wesleyan University
Ignasi Ribas
Institute of Space Studies of Catalonia (IEEC)
Spanish National Research Council (CSIC)
Marek Skarka
Czech Academy of Sciences
Masaryk University
Alexis M. S. Smith
German Aerospace Center (DLR)
Jan Subjak
Charles University
Czech Academy of Sciences
Motohide Tamura
National Institutes of Natural Sciences
University of Tokyo
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 628 A64Exoplanets from space – CHEOPS and PLATO, ESA’s next two projects
Swedish National Space Board (174/18), 2017-01-01 -- 2022-12-31.
Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
Other Physics Topics
Condensed Matter Physics
Roots
Basic sciences
Infrastructure
Onsala Space Observatory
DOI
10.1051/0004-6361/201935505