Top panels: CARMENES NIR spectrum of HD 189733 b taken on 2017 September 07 at 22:06:29 UT (left panel) and a zoom-in on order 40 around 1.524 μm (right panel). The major telluric absorptions by water vapour bands near 0.95, 1.14 and 1.4 μm are prominent. For this plot, the original spectrum, as provided by the CARMENES pipeline, was corrected approximately for the instrument response using an early type telluric standard star from a previous observation; so the decline of the continuum level is mainly due to the decrease of the stellar flux. The V shapes of the continuum level withineach order are instrumental effects, either due to overestimating the blaze function or the background illumination. This effect is mainly caused by the different observational conditions of the calibration star and the target, such as target altitude and background illumination. In our analysis, the instrument response was not applied, instead, we normalised each order of the spectra. The emission features observed at the reddest wavelengths (>1.5 μm) in the left and right panels are telluric emission lines. Bottom panels: atmospheric absorption model of HD 189733 b in the CARMENES NIR spectral range (left panel) and a zoom-in around 1.524 μm (right panel). The contribution of the planetary disc (i.e. opaque at all wavelengths) has been included. The most prominent features are caused by the atmospheric H₂ O bands. The calculations were performed with the pressure-temperature profile of Brogi et al. (2018; see Fig. 3) and a constant H₂O volume mixing ratio of 10⁻⁴. The model was computed at a very high spectral resolution ( ~ 4 × 10⁷) and convolved with the CARMENES line spread function.