Spitzer Phase Curves of KELT-1b and the Signatures of Nightside Clouds in Thermal Phase Observations
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Beatty_2019_AJ_158_166.pdf
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Final Published Version
Author
Beatty, Thomas G.Marley, Mark S.
Gaudi, B. Scott
Colón, Knicole D.
Fortney, Jonathan J.
Showman, Adam P.
Affiliation
Univ Arizona, Dept Planetary SciUniv Arizona, Lunar & Planetary Lab
Univ Arizona, Steward Observ
Univ Arizona, Dept Astron
Issue Date
2019-09-27
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IOP PUBLISHING LTDCitation
Thomas G. Beatty et al 2019 AJ 158 166Journal
ASTRONOMICAL JOURNALRights
Copyright © 2019. The American Astronomical Society. All rights reserved.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
We observed two full orbital phase curves of the transiting brown dwarf KELT- 1b, at 3.6 and 4.5 mu m, using the Spitzer Space Telescope. Combined with previous eclipse data from Beatty et al., we strongly detect KELT-1b's phase variation as a single sinusoid in both bands, with amplitudes of 964 +/- 36 ppm at 3.6 mu m and 979 +/- 54 ppm at 4.5 mu m, and confirm the secondary eclipse depths measured by Beatty et al. We also measure noticeable eastward hotspot offsets of 28 degrees.4 +/- 3 degrees.5 at 3.6 mu m and 18 degrees.6 +/- 5 degrees.2 at 4.5 mu m. Both the day-night temperature contrasts and the hotspot offsets we measure are in line with the trends seen in hot Jupiters, though we disagree with the recent suggestion of an offset trend by Zhang et al. Using an ensemble analysis of Spitzer phase curves, we argue that nightside clouds are playing a noticeable role in modulating the thermal emission from these objects, based on: (1) the lack of a clear trend in phase offsets with equilibrium temperature, (2) the sharp day-night transitions required to have non-negative intensity maps, which also resolves the inversion issues raised by Keating & Cowan, (3) the fact that all the nightsides of these objects appear to be at roughly the same temperature of 1000 K, while the dayside temperatures increase linearly with equilibrium temperature, and (4) the trajectories of these objects on a Spitzer color-magnitude diagram, which suggest colors only explainable via nightside clouds.ISSN
0004-6256Version
Final published versionSponsors
National Aeronautics & Space Administration (NASA); Center for Exoplanets and Habitable Worlds; Pennsylvania State University; Eberly College of Science; Pennsylvania Space Grant Consortiumae974a485f413a2113503eed53cd6c53
10.3847/1538-3881/ab33fc