Greening of the brown-dwarf desert EPIC 212036875b: a 51 M-J object in a 5-day orbit around an F7V star

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  • Carina M. Persson, Chalmers Univ Technol, Chalmers University of Technology, Onsala Space Observ, Dept Space Earth & Environm
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  • Szilard Csizmadia, German Aerosp Ctr, German Aerospace Centre (DLR), Helmholtz Association, Inst Planetary Res
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  • Alexander J. Mustill, Lund Univ, Lund University, Lund Observ, Dept Astron & Theoret Phys
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  • Malcolm Fridlund, Leiden Univ, Leiden University, Leiden Observ
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  • Artie P. Hatzes, Thüringer Landessternwarte Tautenburg
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  • Grzegorz Nowak, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • Iskra Georgieva, Chalmers Univ Technol, Chalmers University of Technology, Onsala Space Observ, Dept Space Earth & Environm
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  • Davide Gandolfi, Univ Torino, University of Turin, Dipartimento Fis
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  • Melvyn B. Davies, Lund Univ, Lund University, Lund Observ, Dept Astron & Theoret Phys
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  • John H. Livingston, Univ Tokyo, University of Tokyo, Sch Sci, Dept Astron, Bunkyo Ku
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  • Enric Palle, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • Pilar Montanes Rodriguez, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • Michael Endl, Univ Texas Austin, University of Texas System, University of Texas Austin, McDonald Observ
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  • Teruyuki Hirano, Tokyo Inst Technol, Tokyo Institute of Technology, Dept Earth & Planetary Sci, Meguro Ku
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  • Jorge Prieto-Arranz, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • Judith Korth, Univ Cologne, University of Cologne, Rhein Inst Umweltforsch
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  • Sascha Grziwa, Univ Cologne, University of Cologne, Rhein Inst Umweltforsch
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  • Massimiliano Esposito, Thüringer Landessternwarte Tautenburg
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  • Simon Albrecht
  • Marshall C. Johnson, Ohio State Univ, Ohio State University, Dept Astron
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  • Oscar Barragan, Univ Oxford, University of Oxford, Subdept Astrophys, Dept Phys
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  • Hannu Parviainen, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • Vincent Van Eylen, Princeton Univ, Princeton University, Dept Astrophys Sci
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  • Roi Alonso Sobrino, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • Paul G. Beck, Karl Franzens Univ Graz, University of Graz, Inst Phys Geophys Astrophys & Meteorol
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  • Juan Cabrera, German Aerosp Ctr, German Aerospace Centre (DLR), Helmholtz Association, Inst Planetary Res
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  • Ilaria Carleo, Wesleyan Univ, Wesleyan University, Van Vleck Observ
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  • William D. Cochran, Univ Texas Austin, University of Texas System, University of Texas Austin, McDonald Observ
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  • Fei Dai, MIT, Massachusetts Institute of Technology (MIT), Kavli Inst Astrophys & Space Res
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  • Hans J. Deeg, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • Jerome P. de Leon, Univ Tokyo, University of Tokyo, Sch Sci, Dept Astron, Bunkyo Ku
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  • Philipp Eigmueller, German Aerosp Ctr, German Aerospace Centre (DLR), Helmholtz Association, Inst Planetary Res
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  • Anders Erikson, German Aerosp Ctr, German Aerospace Centre (DLR), Helmholtz Association, Inst Planetary Res
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  • Akai Fukui, Natl Astron Observ Japan, National Astronomical Observatory of Japan, National Institutes of Natural Sciences (NINS) - Japan, Okayama Astrophys Observ
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  • Lucia Gonzalez-Cuesta, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • Eike W. Guenther, Thüringer Landessternwarte Tautenburg
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  • Diego Hidalgo, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • Maria Hjorth
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  • Petr Kabath, Czech Acad Sci, Czech Academy of Sciences, Astronomical Institute of the Czech Academy of Sciences, Astron Inst
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  • Emil Knudstrup
  • Nobuhiko Kusakabe, Natl Inst Nat Sci, National Institutes of Natural Sciences (NINS) - Japan, Astrobiol Ctr
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  • Kristine W. F. Lam, TU Berlin, Technical University of Berlin, Ctr Astron & Astrophys
  • ,
  • Mikkel N. Lund
  • Rafael Luque, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • Savita Mathur, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • Felipe Murgas, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • Norio Narita, JST, Japan Science & Technology Agency (JST), PRESTO, Bunkyo Ku
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  • David Nespral, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • Prajwal Niraula, MIT, Massachusetts Institute of Technology (MIT), Dept Earth Atmospher & Planetary Sci
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  • A. O. Henrik Olofsson, Chalmers Univ Technol, Chalmers University of Technology, Onsala Space Observ, Dept Space Earth & Environm
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  • Martin Paetzold, Univ Cologne, University of Cologne, Rhein Inst Umweltforsch
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  • Heike Rauer, TU Berlin, Technical University of Berlin, Ctr Astron & Astrophys
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  • Seth Redfield, Wesleyan Univ, Wesleyan University, Van Vleck Observ
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  • Ignasi Ribas, Univ Barcelona, Institut d'Estudis Espacials de Catalunya (IEEC), University of Barcelona, Inst Ciencies Cosmos, IEEC UB
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  • Marek Skarka, Masaryk Univ, Masaryk University Brno, Dept Theoret Phys & Astrophys
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  • Alexis M. S. Smith, German Aerosp Ctr, German Aerospace Centre (DLR), Helmholtz Association, Inst Planetary Res
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  • Jan Subjak, Charles Univ Prague, Charles University Prague, Czech Academy of Sciences, Astronomical Institute of the Czech Academy of Sciences, Fac Math & Phys, Astron Inst
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  • Motohide Tamura, Natl Inst Nat Sci, National Institutes of Natural Sciences (NINS) - Japan, Astrobiol Ctr

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.

OriginalsprogEngelsk
Artikelnummer64
TidsskriftAstronomy & Astrophysics
Vol/bind628
Antal sider14
ISSN1432-0746
DOI
StatusUdgivet - 8 aug. 2019

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