TESS Full Orbital Phase Curve of the WASP-18b System

Shporer, Avi and Wong, Ian and Huang, Chelsea X. ORCID: https://orcid.org/0000-0003-0918-7484 and Line, Michael R. and Stassun, Keivan G. and Fetherolf, Tara and Kane, Stephen R. and Bouma, Luke G. and Daylan, Tansu and Gunther, Maximilian N. and Ricker, George R. and Latham, David W. and Vanderspek, Roland and Seager, Sara and Winn, Joshua N. and Jenkins, Jon M. and Glidden, Ana and Berta-Thompson, Zach and Ting, Eric B. and Li, Jie and Haworth, Kari (2019) TESS Full Orbital Phase Curve of the WASP-18b System. The Astronomical Journal, 157 (5):178. pp. 1-12. ISSN 0004-6256

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We present a visible-light full orbital phase curve of the transiting planet WASP-18b measured by the TESS mission. The phase curve includes the transit, secondary eclipse, and sinusoidal modulations across the orbital phase shaped by the planet's atmospheric characteristics and the star-planet gravitational interaction. We measure the beaming (Doppler boosting) and tidal ellipsoidal distortion phase modulations and show that the amplitudes of both agree with theoretical expectations. We find that the light from the planet's dayside hemisphere occulted during secondary eclipse, with a relative brightness of 341-18 +17 ppm, is dominated by thermal emission, leading to an upper limit on the geometric albedo in the TESS band of 0.048 (2σ). We also detect the phase modulation due to the planet's atmosphere longitudinal brightness distribution. We find that its maximum is well aligned with the substellar point to within 2.°9 (2σ). We do not detect light from the planet's nightside hemisphere, with an upper limit of 43 ppm (2σ), which is 13% of the dayside brightness. The low albedo, lack of atmospheric phase shift, and inefficient heat distribution from the day to night hemispheres that we deduce from our analysis are consistent with theoretical expectations and similar findings for other strongly irradiated gas giant planets. This work demonstrates the potential of TESS data for studying the full orbital phase curves of transiting systems. Finally, we complement our study by looking for transit timing variations (TTVs) in the TESS data combined with previously published transit times, although we do not find a statistically significant TTV signal.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version deposited in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 01 Apr 2022 01:06
Last Modified: 13 Apr 2022 00:34
Uncontrolled Keywords: planetary systems; planets and satellites: atmospheres; stars: individual (WASP-18, TIC 100100827, TOI 185); Astrophysics - Earth and Planetary Astrophysics; Astrophysics - Solar and Stellar Astrophysics
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Identification Number or DOI: https://doi.org/10.3847/1538-3881/ab0f96
URI: http://eprints.usq.edu.au/id/eprint/47379

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