The LEECH Exoplanet Imaging Survey: Characterization of the Coldest Directly Imaged Exoplanet, GJ 504 b, and Evidence for Superstellar Metallicity - Archive ouverte HAL Access content directly
Journal Articles The Astrophysical Journal Year : 2016

The LEECH Exoplanet Imaging Survey: Characterization of the Coldest Directly Imaged Exoplanet, GJ 504 b, and Evidence for Superstellar Metallicity

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Andrew J. Skemer
  • Function : Author
Caroline V. Morley
  • Function : Author
Neil T. Zimmerman
  • Function : Author
Michael F. Skrutskie
  • Function : Author
Jarron Leisenring
  • Function : Author
Esther Buenzli
  • Function : Author
Vanessa Bailey
  • Function : Author
Philip Hinz
  • Function : Author
Denis Defrére
  • Function : Author
Simone Esposito
Dániel Apai
  • Function : Author
Beth Biller
  • Function : Author
Wolfgang Brandner
  • Function : Author
Laird Close
  • Function : Author
Justin R. Crepp
  • Function : Author
Robert J. de Rosa
  • Function : Author
Silvano Desidera
  • Function : Author
Josh Eisner
  • Function : Author
Jonathan Fortney
  • Function : Author
Richard Freedman
  • Function : Author
Thomas Henning
Karl-Heinz Hofmann
  • Function : Author
Taisiya Kopytova
  • Function : Author
Roxana Lupu
  • Function : Author
Anne-Lise Maire
  • Function : Author
Jared R. Males
  • Function : Author
Mark Marley
Katie Morzinski
  • Function : Author
Jenny Patience
  • Function : Author
Abhijith Rajan
  • Function : Author
George Rieke
  • Function : Author
Dieter Schertl
  • Function : Author
Joshua Schlieder
Jordan Stone
  • Function : Author
Kate Su
  • Function : Author
Amali Vaz
  • Function : Author
Channon Visscher
  • Function : Author
Kimberly Ward-Duong
  • Function : Author
Gerd Weigelt
  • Function : Author
Charles E. Woodward
  • Function : Author

Abstract

As gas giant planets and brown dwarfs radiate away the residual heat from their formation, they cool through a spectral type transition from L to T, which encompasses the dissipation of cloud opacity and the appearance of strong methane absorption. While there are hundreds of known T-type brown dwarfs, the first generation of directly imaged exoplanets were all L type. Recently, Kuzuhara et al. announced the discovery of GJ 504 b, the first T dwarf exoplanet. GJ 504 b provides a unique opportunity to study the atmosphere of a new type of exoplanet with a ∼500 K temperature that bridges the gap between the first directly imaged planets (∼1000 K) and our own solar system's Jupiter (∼130 K). We observed GJ 504 b in three narrow L-band filters (3.71, 3.88, and 4.00 μm), spanning the red end of the broad methane fundamental absorption feature (3.3 μm) as part of the LBTI Exozodi Exoplanet Common Hunt (LEECH) exoplanet imaging survey. By comparing our new photometry and literature photometry with a grid of custom model atmospheres, we were able to fit GJ 504 b's unusual spectral energy distribution for the first time. We find that GJ 504 b is well fit by models with the following parameters: Teff = 544 ± 10 K, g < 600 m s-2, [M/H] = 0.60 ± 0.12, cloud opacity parameter of fsed = 2-5, R = 0.96 ± 0.07 RJup, and log(L) = -6.13 ± 0.03 L, implying a hot start mass of 3-30 Mjup for a conservative age range of 0.1-6.5 Gyr. Of particular interest, our model fits suggest that GJ 504 b has a superstellar metallicity. Since planet formation can create objects with nonstellar metallicities, while binary star formation cannot, this result suggests that GJ 504 b formed like a planet, not like a binary companion.

The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are the University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrophisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and the Research Corporation, on behalf of the University of Notre Dame, University of Minnesota, and University of Virginia.

Dates and versions

insu-03691571 , version 1 (09-06-2022)

Identifiers

Cite

Andrew J. Skemer, Caroline V. Morley, Neil T. Zimmerman, Michael F. Skrutskie, Jarron Leisenring, et al.. The LEECH Exoplanet Imaging Survey: Characterization of the Coldest Directly Imaged Exoplanet, GJ 504 b, and Evidence for Superstellar Metallicity. The Astrophysical Journal, 2016, 817, ⟨10.3847/0004-637X/817/2/166⟩. ⟨insu-03691571⟩
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