Europlanet Science Congress 2021
Virtual meeting
13 – 24 September 2021
Europlanet Science Congress 2021
Virtual meeting
13 September – 24 September 2021
EPSC Abstracts
Vol. 15, EPSC2021-222, 2021, updated on 21 Jul 2021
European Planetary Science Congress 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Detection of OH at the evening terminator of the ultra-hot Jupiter WASP-76b

Rico Landman1, Alejandro Sánchez-López1, Paul Mollière2, Aurora Kesseli1, Amy Louca1, and Ignas Snellen1
Rico Landman et al.
  • 1Leiden University, Leiden Observatory, Netherlands (
  • 2Max-Planck-Institut für Astronomie, Heidelberg, Germany

Ultra-hot Jupiters have dayside temperatures similar to those of M-dwarfs. While molecular absorption from the hydroxyl radical (OH) is easily observed in near-infrared spectra of M-dwarfs, it is often not considered when studying the atmospheres of (ultra-)hot Jupiters. We use high-resolution spectroscopic near-infrared observations of a transit of WASP-76b obtained using CARMENES to assess the presence of OH. After validating the OH line list, we generate model transit spectra of WASP-76b with petitRADTRANS. The data are corrected for telluric contamination and cross-correlated with the model spectra. After combining all cross-correlation functions from the transit, a detection map is constructed. OH is detected in the atmosphere of WASP-76b with a signal-to-noise ratio of 6.1. From a Markov Chain Monte Carlo retrieval we obtain Kp=234 km/s and a blueshift of 13.9 km/s. Considering the fast spin-rotation of the planet, the OH signal is best explained with the signal mainly originating from the evening terminator and the presence of a strong day- to nightside wind. The signal appears to be broad, with a full width at half maximum of 16.2 km/s. The retrieval results in a weak constraint on the temperature of 2420-3150 K at the pressure of the OH signal. Our results demonstrate that OH is readily observable in the transit spectra of ultra-hot Jupiters. Studying this molecule can give new insights in the molecular dissociation processes in the atmospheres of such planets.

How to cite: Landman, R., Sánchez-López, A., Mollière, P., Kesseli, A., Louca, A., and Snellen, I.: Detection of OH at the evening terminator of the ultra-hot Jupiter WASP-76b, European Planetary Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-222,, 2021.