The hot dayside and asymmetric transit of WASP-189 b seen by CHEOPS

Lendl, M.; Csizmadia, Sz.; Deline, A.; Fossati, L.; Kitzmann, D.; Heng, K.; Hoyer, S.; Salmon, S.; Benz, W.; Broeg, C.; Ehrenreich, D.; Fortier, A.; Queloz, D.; Bonfanti, A.; Brandeker, A.; Collier Cameron, A.; Delrez, L.; Garcia Muñoz, A.; Hooton, M. J.; Maxted, P. F. L.; ... (2020). The hot dayside and asymmetric transit of WASP-189 b seen by CHEOPS. Astronomy and astrophysics, 643(A94), A94. EDP Sciences 10.1051/0004-6361/202038677

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The CHEOPS space mission dedicated to exoplanet follow-up was launched in December 2019, equipped with the capacity to perform photometric measurements at the 20 ppm level. As CHEOPS carries out its observations in a broad optical passband, it can provide insights into the reflected light from exoplanets and constrain the short-wavelength thermal emission for the hottest of planets by observing occultations and phase curves. Here, we report the first CHEOPS observation of an occultation, namely, that of the hot Jupiter WASP-189 b, a MP ≈ 2MJ planet orbiting an A-type star. We detected the occultation of WASP-189 b at high significance in individual measurements and derived an occultation depth of dF = 87.9 ± 4.3 ppm based on four occultations. We compared these measurements to model predictions and we find that they are consistent with an unreflective atmosphere heated to a temperature of 3435 ± 27 K, when assuming inefficient heat redistribution. Furthermore, we present two transits of WASP-189 b observed by CHEOPS. These transits have an asymmetric shape that we attribute to gravity darkening of the host star caused by its high rotation rate. We used these measurements to refine the planetary parameters, finding a ~25% deeper transit compared to the discovery paper and updating the radius of WASP-189 b to 1.619 ± 0.021RJ. We further measured the projected orbital obliquity to be λ = 86.4−4.4+2.9°, a value that is in good agreement with a previous measurement from spectroscopic observations, and derived a true obliquity of Ψ = 85.4 ± 4.3°. Finally, we provide reference values for the photometric precision attained by the CHEOPS satellite: for the V = 6.6 mag star, and using a 1-h binning, we obtain a residual RMS between 10 and 17 ppm on the individual light curves, and 5.7 ppm when combining the four visits.

Item Type:

Journal Article (Original Article)


10 Strategic Research Centers > Center for Space and Habitability (CSH)
08 Faculty of Science > Physics Institute
08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute > NCCR PlanetS

UniBE Contributor:

Kitzmann, Daniel; Heng, Kevin; Benz, Willy; Broeg, Christopher; Fortier, Andrea; Hooton, Matthew John; Morris, Brett Michael; Alibert, Yann; Bandy, Timothy John; Beck, Thomas; Busch, Martin-Diego; Cessa, Virginie; Demory, Brice-Olivier; Hernández León, José Eduardo; Kuntzer, Thibault; Malvasio, Luca; Piazza, Daniele; Rieder, Martin; Simon, Attila and Thomas, Nicolas


500 Science
500 Science > 520 Astronomy
500 Science > 530 Physics
600 Technology > 620 Engineering




EDP Sciences




Danielle Zemp

Date Deposited:

15 Apr 2021 11:39

Last Modified:

18 Apr 2021 03:03

Publisher DOI:





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