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: individual: EPIC 212036875

techniques: photometric

stars: fundamental parameters

planetary systems

techniques: radial velocities

Author

Carina Persson

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

Szilard Csizmadia

German Aerospace Center (DLR)

Alexander J. Mustill

Lund University

Malcolm Fridlund

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

Leiden University

Artie P. Hatzes

Thüringer Landessternwarte Tautenburg

Grzegorz Nowak

University of La Laguna

Instituto Astrofisico de Canarias

Iskra Georgieva

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

Davide Gandolfi

University of Turin

Melvyn B. Davies

Lund University

John H. Livingston

University of Tokyo

Enric Palle

University of La Laguna

Instituto Astrofisico de Canarias

Pilar Montanes Rodriguez

University of La Laguna

Instituto Astrofisico de Canarias

Michael Endl

The University of Texas at Austin

Teruyuki Hirano

Tokyo Institute of Technology

Jorge Prieto-Arranz

Instituto Astrofisico 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 Turin

University of Oxford

Hannu Parviainen

Instituto Astrofisico de Canarias

University of La Laguna

Vincent Van Eylen

Princeton University

Roi Alonso Sobrino

Instituto Astrofisico de Canarias

University of La Laguna

Paul G. Beck

University of Graz

University of La Laguna

Instituto Astrofisico de Canarias

Juan Cabrera

German Aerospace Center (DLR)

Ilaria Carleo

Wesleyan University

William D. Cochran

The University of Texas at Austin

Fei Dai

Massachusetts Institute of Technology (MIT)

Princeton University

Hans J. Deeg

Instituto Astrofisico 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

University of La Laguna

Instituto Astrofisico de Canarias

Eike W. Guenther

Thüringer Landessternwarte Tautenburg

Diego Hidalgo

Instituto Astrofisico 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 Astrofisico de Canarias

Savita Mathur

University of La Laguna

Instituto Astrofisico de Canarias

Felipe Murgas

University of La Laguna

Instituto Astrofisico de Canarias

Norio Narita

National Institutes of Natural Sciences

Japan Science and Technology Agency

Instituto Astrofisico de Canarias

University of Tokyo

David Nespral

Instituto Astrofisico de Canarias

University of La Laguna

Prajwal Niraula

Massachusetts Institute of Technology (MIT)

Henrik Olofsson

Chalmers, Space, Earth and Environment, Onsala Space Observatory, Observation Support

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

Czech Academy of Sciences

Charles university

Motohide Tamura

University of Tokyo

National Institutes of Natural Sciences

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 628 A64

Exoplanets from space – CHEOPS and PLATO, ESA’s next two projects

Swedish National Space Board, 2017-01-01 -- 2022-12-31.

Subject Categories

Astronomy, Astrophysics and Cosmology

Other Physics Topics

Condensed Matter Physics

Roots

Basic sciences

Infrastructure

Onsala Space Observatory

DOI

10.1051/0004-6361/201935505

More information

Latest update

9/23/2020