Context. Elemental abundances can be determined from stellar spectra, making it possible to study galactic formation and evolution. Accurate atomic data is essential for the reliable interpretation and modeling of astrophysical spectra. In this work, we perform laboratory studies on neutral aluminium. This element is found, for example, in young, massive stars and it is a key element for tracing ongoing nucleosynthesis throughout the Galaxy. The near-infrared (NIR) wavelength region is of particular importance, since extinction in this region is lower than for optical wavelengths. This makes the NIR wavelength region a better probe for highly obscured regions, such as those located close to the Galactic center.

Aims. We investigate the spectrum of neutral aluminium with the aim to provide oscillator strengths (f-values) of improved accuracy for lines in the NIR and optical regions (670–4200 nm).

Methods. Measurements of high-resolution spectra were performed using a Fourier transform spectrometer and a hollow cathode discharge lamp. The f-values were derived from experimental line intensities combined with published radiative lifetimes.

Results. We report oscillator strengths for 12 lines in the NIR and optical spectral regions, with an accuracy between 2 and 11%, as well as branching fractions for an additional 16 lines.

Ultra-hot Jupiters are tidally locked with their host stars, dividing their atmospheres into a hot dayside and a colder nightside. As the planet moves through transit, different regions of the atmosphere rotate into view, revealing different chemical regimes. Highresolution spectrographs can observe asymmetries and velocity shifts and offer the possibility for time-resolved spectroscopy. The ultra-hot Jupiter WASP-189 b has recently been found to possess a rich transmission spectrum with evidence for atmospheric dynamics and chemical inhomogeneity. In this study, we search for other atoms and molecules in the planet’s transmission spectrum and investigate asymmetric signals. We analysed and combined eight transits of the ultra-hot Jupiter WASP-189 b collected with the HARPS, HARPS-N, ESPRESSO, and MAROON-X high-resolution spectrographs. Using the cross-correlation technique, we searched for neutral and ionised atoms as well as oxides, and we compared the obtained signals to model predictions. We report significant detections for H, Na, Mg, Ca, Ca+, Ti, Ti+, TiO, V, Cr, Mn, Fe, Fe+, Ni, Sr, Sr+, and Ba+. Of these, Sr, Sr+, and Ba+ are detected for the first time in the transmission spectrum of WASP-189 b. In addition, we robustly confirm the detection of titanium oxide based on observations with HARPS and HARPS-N using the follow-up observations performed with MAROON-X and ESPRESSO. By fitting the orbital traces of the detected species by means of time-resolved spectroscopy using a Bayesian framework, we inferred posterior distributions for orbital parameters as well as line shapes. Our results indicate that different species must originate from different regions of the atmosphere to be able to explain the observed time dependence of the signals. Throughout the course of the transit, most signal strengths are expected to increase due to the larger atmospheric scale height at the hotter trailing terminator. For some species, however, we instead observed that the signals weaken, either due to the ionisation of atoms and their ions or the dissociation of molecules on the dayside.

Astronomical infrared observations are of increasing importance for stellar spectroscopy. The analysis of element abundance relies on high-quality observations, stellar models, and ultimately on accurate atomic data. With the growing number of near-IR astronomical observations and surveys, the absence of highaccuracy data is becoming apparent and a severe limiting factor.We run a program to take up the task to provide evaluated, high-accuracy atomic data for important transitions in the near-infrared spectral region, mainly 1-5 microns. A combinations of both experimental and theoretical techniques is used, to provide complete sets of data with a low uncertainty. FTS measurements of a discharge are combined with laser induced fluorescence techniques, and GRASP2k and ATSP2k atomic structure calculations for the theoretical values.