LEECH Exoplanet Imaging Survey: Characterization of the Coldest Directly Imaged Exoplanet, GJ 504 b, and Evidence for Super-Stellar Metallicity

Authors

• Andrew J. Skemer, University of Arizona
• Caroline V. Morley, University of California, Santa Cruz
• Neil T. Zimmerman, Max Planck Institute for Astronomy
• Michael F. Skrutskie, University of Virginia
• Jarron Leisenring, University of Arizona
• Esther Buenzli, Max Planck Institute for Astronomy
• Mickael Bonnefoy, Max Planck Institute for Astronomy
• Vanessa Bailey, University of Arizona
• Philip Hinz, University of Arizona
• Denis Defrere, University of Arizona
• Simone Esposito, Istituto Nazionale di Astrofisica
• Daniel Apai, University of Arizona
• Beth Biller, The University of Edinburgh
• Wolfgang Brandner, Max Planck Institute for Astronomy
• Laird Close, University of Arizona
• Justin R. Crepp, Notre Dame University, Indiana
• Robert J. De Rosa, Arizona State University at the Tempe Campus
• Silvano Desidera, Instituto Nazionale di Astrofisica
• Josh Eisner, University of Arizona
• Jonathan Fortney, University of California, Santa Cruz
• Richard Freedman, NASA Ames Research Center
• Thomas Henning, Max Planck Institute for Astronomy
• Karl-Heinz Hofmann, Max Planck Institute for Radio Astronomy
• Taisiya Kopytova, Max Planck Institute for Astronomy
• Roxana Lupu, NASA Ames Research Center
• Anne-Lise Maire, Instituto Nazionale di Astrofisica
• Jared R. Males, University of Arizona
• Mark Marley, NASA Ames Research Center
• Katie Morzinski, University of Arizona
• Apurva Oza, University of Virginia
• Jenny Patience, Arizona State University at the Tempe Campus
• Abhijith Rajan, Arizona State University at the Tempe Campus
• George Rieke, University of Arizona
• Dieter Schertl, Max Planck Institute for Radio Astronomy
• Joshua Schlieder, NASA Ames Research Center
• Jordan Stone, University of Arizona
• Kate Su, University of Arizona
• Amali Vaz, University of Arizona
• Channon Visscher, Dordt CollegeFollow
• Kimberly Ward-Duong, Arizona State University at the Tempe Campus
• Gerd Weigelt, Max Planck Institute for Radio Astronomy
• Charles E. Woodward, University of Minnesota - Twin Cities

Document Type

Article

Publication Date

2-2016

Department

Physics and Astronomy

Keywords

planets, satellites, atmospheres, stars

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. (2013) 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 LEECH exoplanet imaging survey. By compar-ing our new photometry and literature photometry to 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 follow-ing parameters: Teff =544±10 K, g/s2, [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⊙, im-plying 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 super-stellar metallicity. Since planet formation can create objects with non-stellar metal-licities, while binary star formation cannot, this result suggests that GJ 504 b formed like a planet, not like a binary companion.

Comments

Copyright © Astrophysical Journal 2016

Source Publication Title

Astrophysical Journal

Publisher

American Astronomical Society

Volume

817

Issue

2

First Page

166

Recommended Citation

Skemer, A. J., Morley, C. V., Zimmerman, N. T., Skrutskie, M. F., Leisenring, J., Buenzli, E., Bonnefoy, M., Bailey, V., Hinz, P., Defrere, D., Esposito, S., Apai, D., Biller, B., Brandner, W., Close, L., Crepp, J. R., De Rosa, R. J., Desidera, S., Eisner, J., Fortney, J., Freedman, R., Henning, T., Hofmann, K., Kopytova, T., Lupu, R., Maire, A., Males, J. R., Marley, M., Morzinski, K., Oza, A., Patience, J., Rajan, A., Rieke, G., Schertl, D., Schlieder, J., Stone, J., Su, K., Vaz, A., Visscher, C., Ward-Duong, K., Weigelt, G., & Woodward, C. E. (2016). LEECH Exoplanet Imaging Survey: Characterization of the Coldest Directly Imaged Exoplanet, GJ 504 b, and Evidence for Super-Stellar Metallicity. Astrophysical Journal, 817 (2), 166. Retrieved from https://digitalcollections.dordt.edu/faculty_work/485