Cloud Atlas: Weak Color Modulations Due to Rotation in the Planetary-mass Companion GU Psc b and 11 Other Brown Dwarfs
Journal
Date Issued
2020
Author(s)
Lew, Ben W. P.
•
Apai, Dániel
•
Zhou, Yifan
•
Radigan, Jacqueline
•
Marley, Mark
•
Schneider, Glenn
•
Cowan, Nicolas B.
•
Miles-Páez, Paulo A.
•
Manjavacas, Elena
•
Karalidi, Theodora
•
•
Lowrance, Patrick J.
•
Burgasser, Adam J.
Abstract
Among the greatest challenges in understanding ultracool brown dwarf and exoplanet atmospheres is the evolution of cloud structure as a function of temperature and gravity. In this study, we present the rotational modulations of GU Psc b—a rare mid-T spectral type planetary-mass companion at the end of the L/T spectral type transition. Based on the Hubble Space Telescope/WFC3 1.1-1.67 μm time-series spectra, we observe a quasi-sinusoidal light curve with a peak-to-trough flux variation of 2.7% and a minimum period of 8 h. The rotation-modulated spectral variations are weakly wavelength-dependent, or largely gray between 1.1 and 1.67 μm. The gray modulations indicate that heterogeneous clouds are present in the photosphere of this low-gravity mid-T dwarf. We place the color and brightness variations of GU Psc b in the context of rotational modulations reported for mid-L to late-T dwarfs. Based on these observations, we report a tentative trend: mid-to-late T dwarfs become slightly redder in J - H color with increasing J-band brightness, while L dwarfs become slightly bluer with increasing brightness. If this trend is verified with more T-dwarf samples, it suggests that in addition to the mostly gray modulations, there is a second-order spectral-type dependence on the nature of rotational modulations.
Volume
159
Issue
3
Start page
125
Issn Identifier
0004-6256
Ads BibCode
2020AJ....159..125L
Rights
open.access
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