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

Author(s): Sara Khalafinejad, Karan Molaverdikhani, Jasmina Blecic, M. Mallonn, L. Nortmann, Luca Fossati, Manuel Güdel, Theresa Rank-Lüftinger
Abstract: 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 D₁ and D₂ 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 D₂ and D₁ lines at ~7 and ~3σ significance levels, respectively. We measured a D₂/D₁ 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 D₁ and D₂ 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 D₂ /D₁ ratio because the presence of haze opacity mutes the absorption features.
Organisation(s): Department of Astrophysics
External organisation(s): Landessternwarte Königstuhl (LSW), Max-Planck-Institut für Astronomie, New York University Abu Dhabi, Leibniz-Institut für Astrophysik Potsdam, Georg-August-Universität Göttingen, Science and Operations Department - Science Division (SCI-SC), Österreichische Akademie der Wissenschaften (ÖAW), Open University
Journal: Astronomy & Astrophysics
Volume: 656
No. of pages: 20
ISSN: 0004-6361
DOI: https://doi.org/10.1051/0004-6361/202141191
Publication date: 12-2021
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy, 103004 Astrophysics
Keywords
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/04933776-8c32-4a82-9caf-d2e5c12f78a8

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