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Exploring the Atmospheric Dynamics of the Extreme Ultrahot Jupiter KELT-9b Using TESS Photometry

Wong, Ian and Shporer, Avi and Kitzmann, Daniel and Morris, Brett M. and Heng, Kevin and Hoeijmakers, H. Jens and Demory, Brice-Olivier and Ahlers, John P. and Mansfield, Megan and Bean, Jacob L. and Daylan, Tansu and Fetherolf, Tara and Rodriguez, Joseph E. and Benneke, Björn and Ricker, George R. and Latham, David W. and Vanderspek, Roland and Seager, Sara and Winn, Joshua N. and Jenkins, Jon M. and Burke, Christopher J. and Christiansen, Jessie L. and Essack, Zahra and Rose, Mark E. and Smith, Jeffrey C. and Tenenbaum, Peter and Yahalomi, Daniel (2020) Exploring the Atmospheric Dynamics of the Extreme Ultrahot Jupiter KELT-9b Using TESS Photometry. Astronomical Journal, 160 (2). Art. No. 88. ISSN 1538-3881. doi:10.3847/1538-3881/aba2cb.

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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 650⁺¹⁴₋₁₅ 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Wong, Ian0000-0001-9665-8429
Shporer, Avi0000-0002-1836-3120
Kitzmann, Daniel0000-0003-4269-3311
Morris, Brett M.0000-0003-2528-3409
Heng, Kevin0000-0003-1907-5910
Hoeijmakers, H. Jens0000-0001-8981-6759
Demory, Brice-Olivier0000-0002-9355-5165
Ahlers, John P.0000-0003-2086-7712
Mansfield, Megan0000-0003-4241-7413
Bean, Jacob L.0000-0003-4733-6532
Daylan, Tansu0000-0002-6939-9211
Fetherolf, Tara0000-0002-3551-279X
Rodriguez, Joseph E.0000-0001-8812-0565
Benneke, Björn0000-0001-5578-1498
Ricker, George R.0000-0003-2058-6662
Latham, David W.0000-0001-9911-7388
Vanderspek, Roland0000-0001-6763-6562
Seager, Sara0000-0002-6892-6948
Winn, Joshua N.0000-0002-4265-047X
Jenkins, Jon M.0000-0002-4715-9460
Burke, Christopher J.0000-0002-7754-9486
Christiansen, Jessie L.0000-0002-8035-4778
Essack, Zahra0000-0002-2482-0180
Rose, Mark E.0000-0003-4724-745X
Smith, Jeffrey C.0000-0002-6148-7903
Tenenbaum, Peter0000-0002-1949-4720
Yahalomi, Daniel0000-0003-4755-584X
Additional Information:© 2020 The American Astronomical Society. Received 2019 October 3; revised 2020 June 30; accepted 2020 July 2; published 2020 July 30. Funding for the TESS mission is provided by NASA's Science Mission directorate. This paper includes data collected by the TESS mission that are publicly available from the Mikulski Archive for Space Telescopes (MAST). Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. We thank two anonymous referees for their helpful comments that greatly improved the manuscript. I.W. is supported by a Heising-Simons 51 Pegasi b postdoctoral fellowship. T.D. acknowledges support from MIT's Kavli Institute as a Kavli postdoctoral fellow. M.M. acknowledges funding from a NASA FINESST grant. Work by J.N.W. was partly supported by the Heising-Simons Foundation.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Heising-Simons Foundation51 Pegasi b Fellowship
Massachusetts Institute of Technology (MIT)UNSPECIFIED
Subject Keywords:Hot Jupiters ; Photometry ; Exoplanet astronomy
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Hot Jupiters (753); Photometry (1234); Exoplanet astronomy (486)
Record Number:CaltechAUTHORS:20200831-101612785
Persistent URL:
Official Citation:Ian Wong et al 2020 AJ 160 88
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105163
Deposited By: Tony Diaz
Deposited On:08 Sep 2020 18:53
Last Modified:16 Nov 2021 18:40

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