Probing the atmosphere of WASP-69 b with low- and high-resolution transmission spectroscopy

Publication date: 
Main author: 
Khalafinejad, S.
IAA authors: 
Amado, P. J.;Bauer, F. F.;López-Puertas, M.
Khalafinejad, S.;Molaverdikhani, K.;Blecic, J.;Mallonn, M.;Nortmann, L.;Caballero, J. A.;Rahmati, H.;Kaminski, A.;Sadegi, S.;Nagel, E.;Carone, L.;Amado, P. J.;Azzaro, M.;Bauer, F. F.;Casasayas-Barris, N.;Czesla, S.;von Essen, C.;Fossati, L.;Güdel, M.;Henning, Th.;López-Puertas, M.;Lendl, M.;Lüftinger, T.;Montes, D.;Oshagh, M.;Pallé, E.;Quirrenbach, A.;Reffert, S.;Reiners, A.;Ribas, I.;Stock, S.;Yan, F.;Zapatero Osorio, M. R.;Zechmeister, M.
Astronomy and Astrophysics
Publication type: 
Consideration of both low- and high-resolution transmission spectroscopy is key for obtaining a comprehensive picture of exoplanet atmospheres. In studies of transmission spectra, the continuum information is well established with low-resolution spectra, while the shapes of individual lines are best constrained with high-resolution observations. In this work, we aim to merge high- with low-resolution transmission spectroscopy to place tighter constraints on physical parameters of the atmospheres. We present the analysis of three primary transits of WASP-69 b in the visible (VIS) channel of the CARMENES instrument and perform a combined low- and high-resolution analysis using additional data from HARPS-N, OSIRIS/GTC, and WFC3/HST already available in the literature. We investigate the Na I D<SUB>1</SUB> and D<SUB>2</SUB> doublet, Hα, the Ca II infra-red triplet (IRT), and K I λ7699 Å lines, and we monitor the stellar photometric variability by performing long-term photometric observations with the STELLA telescope. During the first CARMENES observing night, we detected the planet Na I D<SUB>2</SUB> and D<SUB>1</SUB> lines at ~7 and ~3σ significance levels, respectively. We measured a D<SUB>2</SUB>/D<SUB>1</SUB> intensity ratio of 2.5 ± 0.7, which is in agreement with previous HARPS-N observations. Our modelling of WFC3 and OSIRIS data suggests strong Rayleigh scattering, solar to super-solar water abundance, and a highly muted Na feature in the atmosphere of this planet, in agreement with previous investigations of this target. We use the continuum information retrieved from the low-resolution spectroscopy as a prior to break the degeneracy between the Na abundance, reference pressure, and thermosphere temperature for the high-resolution spectroscopic analysis. We fit the Na I D<SUB>1</SUB> and D<SUB>2</SUB> lines individually and find that the posterior distributions of the model parameters agree with each other within 1σ. Our results suggest that local thermodynamic equilibrium processes can explain the observed D<SUB>2</SUB> /D<SUB>1</SUB> ratio because the presence of haze opacity mutes the absorption features.
ADS Bibcode: 
methods: observational;techniques: spectroscopic;planets and satellites: atmospheres;planets and satellites: composition;planets and satellites: individual: WASP-69 b;stars: activity;Astrophysics - Earth and Planetary Astrophysics