High-resolution Doppler-resolved spectroscopy has presented new opportunities for studying the atmospheres of exoplanets. While the ‘classical’ cross-correlation approach has proven to be efficient at finding atmospheric species, it is unable to perform direct atmospheric retrievals. Recent work has shown that retrievals are possible using a direct likelihood evaluation or likelihood ‘mappings’. The unique aspect of high-resolution retrievals is that the data-processing methods required to remove the stellar and telluric lines also distort the underlying exoplanet’s signal and therefore the forward model must be pre-processed to match this filtering. This was the key remaining limitation in our previously published framework. This paper directly addresses this by introducing a simple and fast model-filtering technique that can replicate the processing performed by algorithms such as SysRem and PCA. This enables retrievals to be performed without having to perform expensive injection and pre-processing steps for every model. We show that we can reliably constrain quantitative measures of the atmosphere from transmission spectra including the temperature-pressure profile, relative abundances, planetary velocities and rotational broadening parameters. Finally, we demonstrate our framework using UVES transmission spectroscopy of WASP-121b. We constrain the temperature-pressure profile and relative abundances of Fe, Cr, and V to be log10(χFe/χCr) = 1.66±0.28, log10(χFe/χV) = 3.78±0.29 and log10(χFe/χMg) = -1.26±0.60. The relative abundances are consistent with solar values, with the exception of Fe/Mg, where the large Mg abundance is probably explained by the escaping atmosphere of WASP-121b that is not accounted for in our atmospheric model.

No abstract

No abstract

No abstract

Recent progress in high-resolution transmission spectroscopy has offered new avenues in which to characterise the atmospheres of transiting exoplanets. High-resolution cross-correlation spectroscopy allows for the unambiguous detection of molecules/atoms. It has also been used to map both atmospheric dynamics and longitudinal variations in the abundance of species across the morning and evening limbs. We present multiple VLT/ESPRESSO observations of the ultra-hot Jupiter WASP-121b, from which we constrain relative abundances of various neutral metals consistently across all observations, whilst accounting for the distortion of the exoplanet’s signal caused by traditional data processing techniques. We also constrain planetary orbital velocities and T-P profiles. We compare our abundance constraints with previous constraints using VLT/UVES transmission spectroscopy of WASP-121b, and find our results to be consistent between observations, and also in agreement with stellar values for species previously detected in the atmosphere of WASP-121b. Our retrieval framework can also be used to identify potential exospheric species, resulting in extended absorption features beyond the transit equivalent Roche limit of WASP-121b (ReqRL ∼ 1.3 Rp). Hα, Fe II, and Ca II were found to extend to high altitudes (1.54 ± 0.04 Rp, 1.17 ± 0.01 Rp, and 2.52 ± 0.34 Rp, respectively), which are broadly consistent with literature values. The consistency of our constraints across multiple high-resolution observations is a strong validation of our model filtering and retrieval framework, as well as the stability of the atmosphere over the timescales of months/years, and could allow for planet formation processes to be inferred from future ground-based observations of exoplanetary atmospheres.