Top: bayesian inference of the upper thermospheric conditions of WASP-69 b. Comparison of the best-fit model spectra of Na I D₂ (left panel, shaded green area) and Na I D₁ (middle panel, shaded blue area) with discarded and used high-resolution spectroscopic data in gray and orange, respectively, and retrieved temperature profiles based on the posteriors (right panel). The dashed vertical line in red marks the retrieved temperature using low-resolution spectra (Sect. 4.1). Uncertainties are marked by vertical dashed lines at the 16, 50, and 84% quantiles. Bottom: posterior probability distributionof high-resolution model parameters as well as the marginalized distribution for each parameter for Na D₂ (shaded green area) and D₁ (shaded blue area) in WASP-69 b. The marginalized uncertainties are marked by vertical dashed lines at the 16%, 50%, and 8 4% quantiles. In the density maps, 1σ and 2σ are given as 1 − e^−0.5 ~ 0.393 and 1 −e^−2.0 ~ 0.865, respectively,as is common for multivariate MCMC results.