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Context. Advancements in extreme-precision radial velocity (RV) observations for detecting low-mass exoplanets show that different spectral lines show different behaviours in response to stellar activity. Though this can be dealt with experimentally, why this is the case has not been studied. The Sun is a good test case for testing hypotheses as we can study spatially resolved observations with high-resolution spectropolarimetry to understand spectral line behaviour.

Aims. We aim to investigate whether the difference of spectral line behaviour can be attributed to the height of atoms in the solar atmosphere. It is expected that photospheric spectral lines will act differently from their chromospheric counterparts in response to magnetic fields.

Methods. We used a unique dataset using the CRisp Imaging SpectroPolarimeter (CRISP) looking at three spectral lines, two in the photosphere and one in the chromosphere, and measured their spatially resolved radial velocities, their transversal and longitudinal magnetic fields, their magnetic field strengths, and their source functions. We correlated the magnetic field measurements against the radial velocities and compared them against the case in which we destroyed the spatial resolution to mimic a normal stellar observation with high-resolution spectra.

Results. We find that the unsigned magnetic field is strongly correlated to the RV for both the photospheric and chromospheric spectral lines in the case where the observation is spatially resolved. When the spatial resolution is destroyed, this correlation changes. We find that for the photospheric spectral lines there still exists a correlation to both components of the magnetic field, but the chromospheric spectral lines do not show any significant correlation.

Context: Abundances of M dwarfs, the most numerous stellar type in the Galaxy, can enhance our understanding of planet formation processes. They can also be used to study the chemical evolution of the Galaxy, where α-capture elements play a particularly important role.

Aims: We aim to obtain the abundances of Fe, Ti, and Ca for a small sample of well-known M dwarfs for which interferometric measurements are available. These stars and their abundances are intended to serve as a benchmark for future large-scale spectroscopic studies.

Methods: We analysed spectra obtained with the GIANO-B spectrograph. Turbospectrum and the wrapper TSFitPy were used with MARCS atmospheric models to fit synthetic spectra to the observed spectra. We performed a differential abundance analysis in which we also analysed a solar spectrum using the same method and then subtracted the derived abundances line by line. The median was taken as the final abundance of each element and each star.

Results: Our abundances of Fe, Ti, and Ca mostly agree within the uncertainties with other values from the literature. However, there are few studies to compare with.

Magnetic field investigations of Sun-like stars, using Zeeman splitting of non-polarised spectra, in the optical and H-band have found significantly different magnetic field strengths for the same stars, the cause of which is currently unknown. We aim to further investigate this issue by systematically analysing the magnetic field of ξ Boo A, a magnetically active G7 dwarf, using spectral lines at different wavelengths. We used polarised radiative transfer accounting for the departures from local thermodynamic equilibrium to generate synthetic spectra. To find the magnetic field strengths in the optical, H-band, and K-band, we employed MCMC sampling analysis of high-resolution spectra observed with the spectrographs CRIRES⁺, ESPaDOnS, NARVAL, and UVES. We also determine the formation depth of different lines by calculating the contribution functions for each line employed in the analysis. We find that the magnetic field strength discrepancy between lines in the optical and H-band persists even when treating the different wavelength regions consistently. In addition, the magnetic measurements derived from the K-band appear to more closely align with the optical. The H-band appears to yield magnetic field strengths ~0.4 kG with a statistically significant variation while the optical and K-band is stable at ~0.6 kG for observations spanning about two decades. The contribution functions reveal that the optical lines form at a significantly higher altitude in the photosphere compared to those in the H- and K-band. While we find that the discrepancy remains, the variation of formation depths could indicate that the disagreement between magnetic field measurements obtained at different wavelengths is linked to the variation of the magnetic field along the line of sight and between different structures, such as star spots and faculae, in the stellar photosphere.

Context. General circulation models of gas giant exoplanets predict equatorial jets that drive inhomogeneities in the atmospheric physical parameters across the planetary surface. Aims. We studied the transmission spectrum of the hot Jupiter WASP-127 b during one transit in the K band with CRIRES+. Methods. Telluric and stellar signals were removed from the data using SYSREM and the planetary signal was investigated using the cross-correlation technique. After detecting a spectral signal indicative of atmospheric inhomogeneities, we employed a Bayesian retrieval framework with a two-dimensional modelling approach tailored to address this scenario. Results. We detected strong signals of H2O and CO, which exhibited not one but two distinct cross-correlation peaks. The doublepeaked signal can be explained by a supersonic equatorial jet and muted signals at the planetary poles, with the two peaks representing the signals from the planet's morning and evening terminators. We calculated an equatorial jet velocity of 7.7 +/- 0.2 km s(-1) from our retrieved overall equatorial velocity and the planet's tidally locked rotation, and derive distinct atmospheric properties for the two terminators as well as the polar region. Our retrieval yields a solar C/O ratio and metallicity, and shows that the muted signals from the poles can be explained by either significantly lower temperatures or a high cloud deck. It provides tentative evidence for the morning terminator to be cooler than the evening terminator by -175(-117)(+133) K. Conclusions. Our detection of CO challenges previous non-detections of this species in WASP-127b's atmosphere. The presence of a clear double-peaked signal highlights the importance of taking planetary three-dimensional structure into account during interpretation of atmospheric signals. The measured supersonic jet velocity and the lack of signal from the polar regions, representing a detection of latitudinal inhomogeneity in a spatially unresolved target, showcases the power of high-resolution transmission spectroscopy for the characterisation of global circulation in exoplanet atmospheres.

The ultra-hot Jupiter (UHJ) TOI-2109b marks the lower edge of the equilibrium temperature gap between 3500 and 4500 K, an unexplored thermal regime that separates KELT-9b, the hottest planet yet discovered, from all other currently known gas giants. To study the thermochemical structure of TOI-2109b's atmosphere, we obtained high-resolution emission spectra of both the planetary day- and nightsides with CAHA/CARMENES and VLT/CRIRES+. By applying the cross-correlation technique to the high-resolution spectra, we identified the emission signatures of Fe I (S/N = 4.3) and CO (S/N = 6.3), as well as a thermal inversion layer in the dayside atmo-sphere; no significant H2O signal was detected from the dayside. None of the analyzed species were detectable from the nightside atmosphere. We applied a Bayesian retrieval framework that combines high-resolution spectroscopy with photometric measurements to constrain the dayside atmospheric parameters and derive upper limits for the nightside hemisphere. The dayside thermal inversion extends from approximately 3200 to 4600 K, with an atmospheric metallicity consistent with that of the host star (0.36 dex). Only weak constraints could be placed on the C/O ratio, with a lower limit of 0.15. The retrieved spectral line broadening is consistent with tidally locked rotation, indicating the absence of strong dynamical processes in the atmosphere. An upper temperature limit of approximately 2400 K and a maximum atmospheric temperature gradient of about 700 K/log bar could be derived for the planetary nightside. Comparison of the retrieved dayside temperature-pressure profile with theoretical models, the absence of strong atmospheric dynamics, and significant differences in the thermal constraints between the day- and nightside hemispheres suggest a limited heat transport efficiency across the planetary atmosphere. Overall, our results place TOI-2109b in a transitional regime between the UHJs below the thermal gap, which show both CO and H2O emission lines, and KELT-9b, where molecular features are largely absent.

Context: The extreme temperature gradients from day- to nightside in the atmospheres of hot Jupiters generate fast winds in the form of equatorial jets or day-to-night flows. Observations of blue-shifted and red-shifted signals in the transmission and dayside spectra of WASP-189 b have sparked discussions about the nature of winds on this planet.

Aims: To investigate the structure of winds in the atmosphere of the ultra-hot Jupiter WASP-189 b, we studied its dayside emission spectrum with CRIRES⁺ in the spectral K band.

Methods: After removing stellar and telluric lines, we used the cross-correlation method to search for a range of molecules and detected emission signals of CO and Fe. Subsequently, we employed a Bayesian framework to retrieve the atmospheric parameters relating to the temperature-pressure structure and chemistry, and incorporated a numerical model of the line profile influenced by various dynamic effects to determine the wind structure.

Results: The cross-correlation signals of CO and Fe showed a velocity offset of ∼ 6 km s^-1, which could be caused by a fast day-tonight wind in the atmosphere of WASP-189 b. The atmospheric retrieval showed that the line profile of the observed spectra is best fitted by the presence of a day-to-night wind of 4.4_-2.2^+1.8 km s^-1, while the retrieved equatorial jet velocity of 1.0_-1.8^+0.9 km s^-1 is consistent with the absence of such a jet. Such a wind pattern is consistent with the observed line broadening and can explain the majority of the velocity offset, while uncertainties in the ephemerides and the effects of a hot spot could also contribute to this offset. We further retrieved an inverted temperature-pressure profile, and under the assumption of equilibrium chemistry we retrieved a C/O ratio of 0.32_-0.14^+0.41 and a metallicity of M/H = 1.40_-0.60^+1.39.

Conclusions: We showed that red-shifts of a few km s^-1 in the dayside spectra could be explained by day-to-night winds. Further studies combining transmission and dayside observations could advance our understanding of WASP-189 b's atmospheric circulation by improving the uncertainties in the velocity offset and wind parameters.

Context. High-precision radial velocity (RV) measurements with slit spectrographs require the instrument profile (IP) and Earth's atmospheric spectrum to be known and to be incorporated into the RV calculation. Aims. We developed an RV pipeline, called Velocity and IP EstimatoR (viper), to achieve high-precision RVs in the near-infrared (NIR). The code is able to process observations taken with a gas cell and includes modelling of the IP and telluric lines. Methods. We utilised least-square fitting and telluric forward modelling to account for instrument instabilities and atmospheric absorption lines. As part of this process, we demonstrate the creation of telluric-free stellar spectra. Results. By applying viper to observations obtained with the upgraded CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES+) and a gas absorption cell in the K band, we are able to reach an RV precision of around 3 m/s over a time span of 2.5 years. For observations using telluric lines for the wavelength reference, an RV precision of 10 m/s is achieved. Conclusions. We demonstrate that despite telluric contamination, a high RV precision is possible at NIR wavelengths, even for a slit spectrograph with varying IP. Furthermore, we show that CRIRES+ performs well and is an excellent choice for science studies requiring precise stellar RV measurements in the infrared.

Context. The A-type metallic-line (Am) stars are typically considered to be non-magnetic or to possess very weak sub-G magnetic fields. This view has been repeatedly challenged in the literature; most commonly for the bright hot Am star o Peg. Several studies claim to have detected 1-2 kG field of unknown topology in this object, possibly indicating a new process of magnetic-field generation in intermediate-mass stars. Aims. In this study, we revisit the evidence of a strong magnetic field in o Peg using new high-resolution spectropolarimetric observations and advanced spectral fitting techniques.

Methods. We estimated the mean magnetic field strength in o Peg from the high-precision CRyogenic InfraRed Echelle Spectrograph (CRIRES+) measurement of near-infrared (NIR) sulphur lines. We modelled this observation with a polarised radiative transfer code, including treatment of the departures from local thermodynamic equilibrium. In addition, we used the least-squares deconvolution multi-line technique to derive longitudinal field measurements from archival optical spectropolarimetric observations of this star.

Results. Our analysis of the NIR S I lines reveals no evidence of Zeeman broadening, ruling out magnetic field with a strength exceeding 260 G. This null result is compatible with the relative intensification of Fe II lines in the optical spectrum, taking into account blending and uncertain atomic parameters of the relevant diagnostic transitions. Longitudinal field measurements on three different nights also yield null results with a precision of 2 G.

Conclusions. This study refutes the claims of kG-strength dipolar or tangled magnetic field in o Peg. This star therefore appears to be non-magnetic, with surface magnetic field characteristics no different from those of other Am stars.

With this work we summarise the design evolution and challenges of the Fiber-Link module for ANDES (ArmazoNes high Dispersion Echelle Spectrograph), the high resolution spectrograph for ESO ELT. The instrument just passed the System Architecture Review of Phase-B1. The Fiber-Link subsystem carries and redistributes the light from the telescope to the spectrometers via several selectable optical paths. The general updated layout for the Fiber-Link module is presented giving element characteristics and obtained performances. First results from laboratory test and prototype activities are also shown. Moreover, we include the reasoning for selected solutions and explaining how requirements are met. Finally, we summarise the compliance against the science top-level requirements and the issues to address moving forward.

The first generation of ELT instruments includes an optical-infrared high resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs ([U]BV, RIZ, YJH) providing a spectral resolution of similar to 100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 mu m with the goal of extending it to 0.35-2.4 mu m with the addition of an U arm to the BV spectrograph and a separate K band spectrograph. It operates both in seeing- and diffraction-limited conditions and the fibre-feeding allows several, interchangeable observing modes including a single conjugated adaptive optics module and a small diffraction-limited integral field unit in the NIR. Modularity and fibre-feeding allows ANDES to be placed partly on the ELT Nasmyth platform and partly in the Coude room. ANDES has a wide range of groundbreaking science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars, tests on the stability of Nature's fundamental couplings, and the direct detection of the cosmic acceleration. The ANDES project is carried forward by a large international consortium, composed of 35 Institutes from 13 countries, forming a team of almost 300 scientists and engineers which include the majority of the scientific and technical expertise in the field that can be found in ESO member states.