Exploring the Atmospheric Dynamics of the Extreme Ultrahot Jupiter KELT-9b Using TESS Photometry
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Wong_2020_AJ_160_88.pdf
Description
Published version
Size
1.32 MB
Format
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Checksum (MD5)
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Author(s)
Wong, Ian
Shporer, Avi
Kitzmann, Daniel
Morris, Brett M
Heng, Kevin
Hoeijmakers, H Jens
Demory, Brice-Olivier
Ahlers, John P
Mansfield, Megan
Bean, Jacob L
Date Issued
2020
Journal
Astronomical Journal
Publisher
American Astronomical Society
Version
Final published version
Abstract
© 2020. The American Astronomical Society. All rights reserved.. We carry out a phase-curve analysis of the KELT-9 system using photometric observations from NASA's Transiting Exoplanet Survey Satellite (TESS). The measured secondary eclipse depth and peak-to-peak atmospheric brightness modulation are and 566 16 ppm, respectively. The planet's brightness variation reaches maximum 31 5 minutes before the midpoint of the secondary eclipse, indicating a 5.2 0.9 eastward shift in the dayside hot spot from the substellar point. We also detect stellar pulsations on KELT-9 with a period of 7.58695 0.00091 hr. The dayside emission of KELT-9b in the TESS bandpass is consistent with a blackbody brightness temperature of 4600 100 K. The corresponding nightside brightness temperature is 3040 100 K, comparable to the dayside temperatures of the hottest known exoplanets. In addition, we detect a significant phase-curve signal at the first harmonic of the orbital frequency and a marginal signal at the second harmonic. While the amplitude of the first harmonic component is consistent with the predicted ellipsoidal distortion modulation assuming equilibrium tides, the phase of this photometric variation is shifted relative to the expectation. Placing KELT-9b in the context of other exoplanets with phase-curve observations, we find that the elevated nightside temperature and relatively low day-night temperature contrast agree with the predictions of atmospheric models that include H2 dissociation and recombination. The nightside temperature of KELT-9b implies an atmospheric composition containing about 50% molecular and 50% atomic hydrogen at 0.1 bar, a nightside emission spectrum that deviates significantly from a blackbody, and a 0.5-2.0 μm transmission spectrum that is featureless at low resolution.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
Massachusetts Institute of Technology. Department of Physics
MIT Kavli Institute for Astrophysics and Space Research
Massachusetts Institute of Technology. Department of Aeronautics and Astronautics
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DOI of Published Version
https://doi.org/10.3847/1538-3881/ABA2CB
