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We present initial results from the Dark Energy Spectroscopic Instrument (DESI) complete calibration of the colour–redshift relation (DC3R2) secondary target survey. Our analysis uses 230 k galaxies that overlap with KiDS-VIKING ugriZYJHKs photometry to calibrate the colour–redshift relation and to inform photometric redshift (photo-z) inference methods of future weak lensing surveys. Together with emission line galaxies (ELGs), luminous red galaxies (LRGs), and the Bright Galaxy Survey (BGS) that provide samples of complementary colour, the DC3R2 targets help DESI to span 56 per cent of the colour space visible to Euclid and LSST with high confidence spectroscopic redshifts. The effects of spectroscopic completeness and quality are explored, as well as systematic uncertainties introduced with the use of common Self-Organizing Maps trained on different photometry than the analysis sample. We further examine the dependence of redshift on magnitude at fixed colour, important for the use of bright galaxy spectra to calibrate redshifts in a fainter photometric galaxy sample. We find that noise in the KiDS-VIKING photometry introduces a dominant, apparent magnitude dependence of redshift at fixed colour, which indicates a need for carefully chosen deep drilling fields, and survey simulation to model this effect for future weak lensing surveys.

Stellar active regions like spots and faculae can distort the shapes of spectral lines, inducing variations in the radial velocities that are often orders of magnitude larger than the signals from Earth-like planets. Efforts to mitigate these activity signals have hitherto focused on either the time or the velocity (wavelength) domains. We present a physics-driven Gaussian process (GP) framework to model activity signals directly in time series of line profiles or cross-correlation functions (CCFs). Unlike existing methods that correct activity signals in line profile time series, our approach exploits the time correlation between velocity (wavelength) bins in the line profile variations, and is based on a simplified but physically motivated model for the origin of these variations. When tested on both synthetic and real data sets with signal-to-noise ratios down to ∼100, our method was able to separate the planetary signal from the activity signal, even when their periods were identical. We also conducted injection/recovery tests using two years of realistically sampled HARPS-N solar data, demonstrating the ability of the method to accurately recover a signal induced by a 1.5-Earth mass planet with a semi-amplitude of 0.3 m s−1 and a period of 33 d during high solar activity. [ABSTRACT FROM AUTHOR]

Here, we present the low-resolution transmission spectroscopy of three giant planets using the Himalayan Faint Object Spectrograph Camera (HFOSC) on the 2 m Himalayan Chandra Telescope (HCT) in Hanle, India. It is the first application of transmission spectroscopy with HCT. This study presents results from a single transit, each for three planets: HAT-P-1b, KELT-18b, and WASP-127b. The selection of suitable reference stars assisted in accurately tracking slit losses for the long cadence observations that are needed to achieve the required signal-to-noise ratio (SNR). We employ the common mode correction technique, utilizing a white light transit curve to minimize time-dependent systematic errors. The observed spectra for WASP-127b and HAT-P-1b agree with previous low-resolution transit spectroscopic observations using other observing facilities. We confirm the presence of Rayleigh scattering in the atmosphere of WASP-127b. In addition, we provide the first low-resolution transmission spectrum for KELT-18b. Modelling the exoplanet atmosphere with HFOSC and available IR observations from HST and Spitzer for WASP-127b and HAT-P-1b shows that HFOSC can be an alternative optical instrument to use in conjunction with IR observations to constrain the atmospheric parameters better. [ABSTRACT FROM AUTHOR]

Accurate astrometric and photometric measurements from Gaia have led to the construction of 3D dust extinction maps which can now be used for estimating the integrated extinctions of Galactic sources located within 5 kpc. These maps based on optical observations may not be reliable for use in the ultraviolet (UV) which is more sensitive to reddening. Past studies have focussed on studying UV extinction using main-sequence stars but lack comparison with 3D dust maps. White dwarfs with well-modelled hydrogen-dominated (DA) atmospheres provide an advantage over main-sequence stars affected by magnetic activity. In this work, we study the variation of UV extinction with 3D dust maps utilizing Hubble Space Telescope (HST) and Galaxy Evolution Explorer (GALEX) observations of DA white dwarfs located within 300 pc. We used HST COS spectroscopic data of 76 sightlines to calculate the optical extinction from Si  ii column densities and validate our results with the kinematic model predictions of the local interstellar medium. Also, we combined GALEX and Gaia photometric observations of 1158 DA white dwarfs to study UV reddening by comparing observed and modelled colour–colour relations. We calculated GALEX non-linearity corrections and derived reddening coefficients [ |$R(NUV-G)=6.52\pm 1.53$| and |$R(FUV-G)=6.04\pm 2.41$| ] considering their variations with optical extinction (⁠|$\rm{A_{V}}\lt 0.1$|  mag), and found them to be in good agreement with known extinction laws. HST analysis suggests a positive bias of 0.01–0.02 mag in the optical extinction from 3D maps depending on the Galactic latitude. These results independently confirm the validity of 3D dust maps to de-redden the optical and UV observations of white dwarfs. [ABSTRACT FROM AUTHOR]

The Early Data Release (EDR) of the Dark Energy Spectroscopic Instrument (DESI) comprises spectroscopy obtained from 2020 December 14 to 2021 June 10. White dwarfs were targeted by DESI both as calibration sources and as science targets and were selected based on Gaia photometry and astrometry. Here, we present the DESI EDR white dwarf catalogue, which includes 2706 spectroscopically confirmed white dwarfs of which approximately 60 per cent have been spectroscopically observed for the first time, as well as 66 white dwarf binary systems. We provide spectral classifications for all white dwarfs, and discuss their distribution within the Gaia Hertzsprung–Russell diagram. We provide atmospheric parameters derived from spectroscopic and photometric fits for white dwarfs with pure hydrogen or helium photospheres, a mixture of those two, and white dwarfs displaying carbon features in their spectra. We also discuss the less abundant systems in the sample, such as those with magnetic fields, and cataclysmic variables. The DESI EDR white dwarf sample is significantly less biased than the sample observed by the Sloan Digital Sky Survey, which is skewed to bluer and therefore hotter white dwarfs, making DESI more complete and suitable for performing statistical studies of white dwarfs. [ABSTRACT FROM AUTHOR]

Context. The kinematic information of the extraplanar diffuse ionized gas (eDIG) around galaxies provides clues to the origin of the gas. Aims. The eDIG-CHANGES project studies the physical and kinematic properties of the eDIG around the CHANG-ES sample of nearby edge-on disk galaxies. Methods. We use a novel multi-slit narrow-band spectroscopy technique to obtain the spatial distribution of the spectral properties of the ionized gas around NGC 891, which is often regarded as an analogue of the Milky Way. We developed specific data reduction procedures for the multi-slit narrow-band spectroscopy data taken with the MDM 2.4 m telescope. The data presented in this paper cover the Hα and [N II]λλ6548, 6583 Å emission lines. Results. The eDIG traced by the Hα and [N II] lines shows an obvious asymmetric morphology, being brighter in the northeastern part of the galactic disk and extending a few kiloparsecs above and below the disk. Global variations in the [N II]/Hα line ratio suggest additional heating mechanisms for the eDIG at large heights beyond photoionization. We also construct position-velocity (PV) diagrams of the eDIG based on our optical multi-slit spectroscopy data and compare them to similar PV diagrams constructed with the H I data. The dynamics of the two gas phases are generally consistent with each other. Modelling the rotation curves at different heights from the galactic mid-plane suggests a vertical negative gradient in turnover radius and maximum rotation velocity, with magnitudes of approximately 3 kpc kpc−1 and 22 − 25 km s−1 kpc−1, respectively. Conclusions. Our measured vertical gradients of the rotation curve parameters suggest significant differential rotation of the ionized gas in the halo, often referred to as the lagging eDIG. Systematic study of the lagging eDIG, using the multi-slit narrow-band spectroscopy technique developed in our eDIG-CHANGES project, will help us to better understand the dynamics of the ionized gas in the halo. [ABSTRACT FROM AUTHOR]

Context. EX Lupi is the prototype of EX Lup-type stars, which are classical T Tauri stars (cTTSs) with luminosity bursts and outbursts of 1–5 magnitudes that last for a few months to a few years. These events are ascribed to an episodic accretion that can occur repeatedly, but whose physical mechanism is still debated. Aims. We aim to investigate the magnetically driven accretion of EX Lup in quiescence. We include for the first time a study of the small- and large-scale magnetic field. This allows us to characterise the magnetospheric accretion process of the system completely. Methods. We used spectropolarimetric times series acquired in 2016 and 2019 with the Echelle SpectroPolarimetric Device for the Observation of Stars and in 2019 with the SpectroPolarimètre InfraRouge at the Canada-France-Hawaii telescope during a quiescence phase of EX Lup. We were thus able to perform a variability analysis of the radial velocity, the emission lines, and the surface-averaged longitudinal magnetic field in different epochs and wavelength domains. We also provide a small-scale magnetic field analysis using Zeeman intensification of photospheric lines and a large-scale magnetic topology reconstruction using Zeeman-Doppler imaging. Results. Our study reveals that typical magnetospheric accretion is ongoing on EX Lup. A main accretion funnel flow connects the inner disc to the star in a stable fashion and produces an accretion shock on the stellar surface close to the pole of the magnetic dipole component. We also measure one of the strongest fields ever observed on cTTSs. This strong field indicates that the disc is truncated by the magnetic field close to but beyond the corotation radius, where the angular velocity of the disc equals the angular velocity of the star. This configuration is suitable for a magnetically induced disc instability that yields episodic accretion onto the star. [ABSTRACT FROM AUTHOR]

The Calar Alto Void Integral-field Treasury surveY (CAVITY) is a legacy project aimed at characterising the population of galaxies inhabiting voids, which are the most under-dense regions of the cosmic web, located in the Local Universe. This paper describes the first public data release (DR1) of CAVITY, comprising science-grade optical data cubes for the initial 100 out of a total of ~300 galaxies in the Local Universe (0.005 < z < 0.050). These data were acquired using the integral-field spectrograph PMAS/PPak mounted on the 3.5m telescope at the Calar Alto observatory. The DR1 galaxy sample encompasses diverse characteristics in the color-magnitude space, morphological type, stellar mass, and gas ionisation conditions, providing a rich resource for addressing key questions in galaxy evolution through spatially resolved spectroscopy. The galaxies in this study were observed with the low-resolution V500 set-up, spanning the wavelength range 3745-7500 Å, with a spectral resolution of 6.0 Å (FWHM). Here, we describe the data reduction and characteristics and data structure of the CAVITY datasets essential for their scientific utilisation, highlighting such concerns as vignetting effects, as well as the identification of bad pixels and management of spatially correlated noise. We also provide instructions for accessing the CAVITY datasets and associated ancillary data through the project's dedicated database. [ABSTRACT FROM AUTHOR]

Context. Hot subdwarf stars are compact blue evolved objects, burning helium in their cores surrounded by a tiny hydrogen envelope. In the Hertzsprung-Russell Diagram they are located by the blue end of the Horizontal Branch. Most models agree on a quite probable common envelope binary evolution scenario in the Red Giant phase. However, the current binarity rate for these objects is yet unsolved, but key, question in this field. Aims. This study aims to develop a novel classification method for identifying hot subdwarf binaries within large datasets using Artificial Intelligence techniques and data from the third Gaia data release (GDR3). The results will be compared with those obtained previously using Virtual Observatory techniques on coincident samples. Methods. The methods used for hot subdwarf binary classification include supervised and unsupervised machine learning techniques. Specifically, we have used Support Vector Machines (SVM) to classify 3084 hot subdwarf stars based on their colour-magnitude properties. Among these, 2815 objects have Gaia DR3 BP/RP spectra, which were classified using Self-Organizing Maps (SOM) and Convolutional Neural Networks (CNN). In order to ensure spectral quality, previously to SOM and CNN classification, our 2815 BP/RP set were pre-analysed with two different approaches: the cosine similarity technique and the Uniform Manifold Approximation and Projection (UMAP) technique. Additional analysis onto a golden sample of 88 well-defined objects, is also presented. Results. The findings demonstrate a high agreement level (∼70–90%) with the classifications from the Virtual Observatory Sed Analyzer (VOSA) tool. This shows that the SVM, SOM, and CNN methods effectively classify sources with an accuracy comparable to human inspection or non-AI techniques. Notably, SVM in a radial basis function achieves 70.97% reproducibility for binary targets using photometry, and CNN reaches 84.94% for binary detection using spectroscopy. We also found that the single–binary differences are especially observable on the infrared flux in our Gaia DR3 BP/BR spectra, at wavelengths larger than ∼700 nm. Conclusions. We find that all the methods used are in fairly good agreement and are particularly effective to discern between single and binary systems. The agreement is also consistent with the results previously obtained with VOSA. In global terms, considering all quality metrics, CNN is the method that provides the best accuracy. The methods also appear effective for detecting peculiarities in the spectra. While promising, challenges in dealing with uncertain compositions highlight the need for caution, suggesting further research is needed to refine techniques and enhance automated classification reliability, particularly for large-scale surveys. [ABSTRACT FROM AUTHOR]

The star β Pictoris is widely known for harbouring a large population of exocomets, which create variable absorption signatures in the stellar spectrum as they transit the star. Although the physical and chemical properties of these objects have long been elusive, the recently developed exocomet curve of growth technique has, for the first time, enabled estimates of exocometary column densities and excitation temperatures, based on absorption measurements in mutliple spectral lines. Using this new tool, we present a refined study of a β Pic exocomet observed on December 6, 1997 with the Hubble Space Telescope. We first show that the comet's signature in Fe II lines is well explained by the transit of two gaseous components, with different covering factors and opacities. Then, we show that the studied comet is detected in the lines of other species, such as Ni II and Cr II. These species are shown to experience similar physical conditions as Fe II (same radial velocity profiles and same excitation temperatures), hinting that they are well mixed. Finally, using almost 100 Fe II lines rising from energy levels between 0 and 33 000 cm–1, we derive the complete excitation diagram of Fe+ in the comet. The transiting gas is found to be populated at an excitation temperature of 8190 ± 160 K, very close to the stellar effective temperature (8052 K). Using a model of radiative and collisional excitation, we show that the observed excitation diagram is compatible with a radiative regime, associated with a close transit distance (≤60 R⋆ ∼ 0.43 au) and a low electronic density (≤107 cm–3). In this regime, the excitation of Fe+ is controlled by the stellar flux, and does not depend on the local electronic temperature or density. These results allow us to derive the Ni+/Fe+ and Cr+/Fe+ ratios in the December 6, 1997 comet, at 8.5 ± 0.8 ⋅ 10–2 and 1.04 ± 0.15 ⋅10–2, respectively, close to solar abundances. [ABSTRACT FROM AUTHOR]

Context. Accretion among planetary mass companions is a poorly understood phenomenon, due to the lack of both observational and theoretical studies. The detection of emission lines from accreting gas giants facilitates detailed investigations into this process. Aims. This work presents a detailed analysis of Balmer lines from one of the few known young, planetary-mass objects with observed emission, the isolated L2γ dwarf 2MASS J11151597+1937266 with a mass between 7 and 21 MJup and an age of 5–45 Myr, located at 45 ± 2 pc. Methods. We obtained the first high-resolution (R ~ 50 000) spectrum of the target with VLT/UVES, an echelle spectrograph operating in the near-ultraviolet to visible wavelengths (3200–6800 Å). Results. We report several resolved hydrogen (H I; H3–H6) and helium (He I; λ5875.6) emission lines in the spectrum. Based on the asymmetric line profiles of Hα and Hβ, the 10% width of Hα (199 ± 1 km s−1), tentative He Iλ6678 emission, and indications of a disk from mid-infrared excess, we confirm ongoing accretion at this object. Using the Gaia update of the parallax, we revise its temperature to 1816 ± 63 K and radius to 1.5 ± 0.1 RJup. Analysis of observed H I profiles using a 1D planet-surface shock model implies a pre-shock gas velocity, v0 = 120−40+ 80 km s−1, and a pre-shock density, log(n0/cm−3) = 14−5+ 0. The pre-shock velocity points to a mass, Mp = 6−4+ 8MJup, for the target. Combining H I line luminosities (Lline) and planetary Lline−Lacc (accretion luminosity) scaling relations, we derived a mass accretion rate, Ṁacc = 1.4−0.9+ 2.8 × 10−8MJup yr−1. Conclusions. The line-emitting area predicted from the planet-surface shock model is very small (~0.03%), and points to a shock at the base of a magnetospherically induced funnel. The Hα profile exhibits a much stronger flux than predicted by the model that best fits the rest of the H I profiles, indicating that another mechanism than shock emission contributes to the Hα emission. Comparison of line fluxes and Ṁacc from archival moderate-resolution SDSS spectra indicate variable accretion at 2MASS J11151597+1937266. [ABSTRACT FROM AUTHOR]

Thanks to their short orbital periods and hot extended atmospheres, hot Jupiters are ideal candidates for atmosphere studies with high- resolution spectroscopy. New stable spectrographs help improve our understanding of the evolution and composition of those types of planets. By analyzing two nights of observations using the ESPRESSO high-resolution spectrograph, we studied the architecture and atmosphere of hot Jupiter WASP-122b (KELT-14b). By analyzing the Rossiter-McLaughlin (RM) effect, we measured the spin-orbit angle of the system to be λ = 0.09−0.90+0.88 deg. This result is in line with literature obliquity measurements of planetary systems around stars with effective temperatures cooler than 6500 K. Using the transmission spectroscopy, we studied the atmosphere of the planet. Applying both the single-line analysis and the cross-correlation method, we looked for Ca I, Cr I, FeH, Fe I, Fe II, H2O, Li I, Mg I, Na I, Ti I, TiO, V I, VO, and Y I. Our results show no evidence of any of these species in WASP-122b's atmosphere. The lack of significant detections can be explained by either the RM effect covering the regions where the atmospheric signal is expected and masking it, along with the low signal-to-noise ratio (S/N) of the observations or the absence of the relevant species in its atmosphere. [ABSTRACT FROM AUTHOR]

Context. The spectra of fast-rotating A-type stars have strongly broadened absorption lines. This effect causes blending of the absorption lines, hindering the measurement of the abundances of the elements that are in the stellar photosphere. Aims. As the exoplanet transits across its host star, it obscures the stellar spectrum that is emitted from directly behind the planet. We aim to extract this obscured spectrum because it is less affected by rotational broadening, resolving the blending of weak lines of elements that would otherwise remain inaccessible. This allows us to more precisely measure the metal abundances in ultra-hot Jupiter systems, many of which have fast-rotating host stars. Methods. We developed a novel method that isolates the stellar spectra behind the planet during a spectral time series, and reconstructs the disc-integrated non-broadened spectrum of the host star. We have systematically tested this method with model-generated spectra of the transit of WASP-189 b across its fast-rotating A-type host star, assessing the effects of limb-darkening, the choice of absorption lines, and the signal-to-noise regime; and demonstrating the sensitivity to photospheric parameters (Teff and log g) and elemental abundances. We applied the method to observations by the HARPS high-resolution spectrograph. Results. For WASP-189, we obtain the metallicity and photospheric abundances for several species previously not reported in literature, Mg, Ca, and Ti, with a significantly improved accuracy compared to the ordinary broadened stellar spectrum. This method can be generally applied to other transiting systems in which abundance determinations via spectral synthesis are imprecise due to severe line blending. It is important to accurately determine the photospheric properties of exoplanet host stars, as it can provide further insight into the formation and evolution of the planets. [ABSTRACT FROM AUTHOR]

Extremely metal-poor (EMPs, [Fe/H] < −3.0) and carbon-enhanced EMP (CE-EMP, [Fe/H] < −3.0 and [C/Fe]>  + 1.0) stars are crucial for understanding the chemical evolution and early formation of the galaxies. Current research on EMP stars is limited by small samples, and ultraviolet (UV) band spectra are lacking. The China Space Station Telescope (CSST) will provide high-quality, low-resolution spectra across wavelengths from near-ultraviolet to near-infrared, with a limiting magnitude of about 21 mag. These will help in identifying EMPs and CE-EMP candidates in the distant Milky Way and nearby galaxies. The present study first uses the simulated CSST spectra to quantitatively evaluate the contribution of UV band spectra in predicting [Fe/H], [α/Fe], and [C/Fe]. The results indicate that UV band spectra reduce the mean absolute error by 0.04, 0.04, and 0.03, respectively, with a σ of 0.02, 0.03, and 0.04, respectively. Further spectral analysis reveals that the EMP stars show unique spectral-line features in the UV band, with significant differences compared to stars of higher metallicity, which could help in identifying EMP stars. Additionally, we tested the impact of UV band spectra on identifying EMP and CE-EMP stars at different noise levels and find that models including UV band spectra improve the identification of EMP and CE-EMP stars in terms of accuracy, recall, and F1 score. At low signal-to-noise ratio (S/N), the model including the UV band achieves a recall of 0.94, significantly higher than the model without the UV band (Recall = 0.48), doubling the capability to identify EMP stars. As the S/N increases, the inclusion of the UV band maintains high recall. This suggests that UV spectra in future large surveys could reduce the risk of missing potentially interesting stellar candidates, ensuring a more comprehensive identification of all possible EMP and CE-EMP star candidates. [ABSTRACT FROM AUTHOR]

Context. The Gaia mission has opened up a new era for the precise astrometry of stars, thus revolutionizing our understanding of the Milky Way. However, beyond a few kiloparseconds from the Sun, parallax measurements become less reliable, and even within 2 kpc, there still exist stars with large uncertainties. Aims. Our aim was to determine the distance and stellar parameters of 521 424 solar-like stars from LAMOST DR9; these stars lacked precise distance measurements (uncertainties higher than 20% or even without any distance estimations) when checked with Gaia. Methods. We proposed a convolutional neural network (CNN) model to predict the absolute magnitudes, colors, and stellar parameters (Teff, log ɡ, and [Fe/H]) directly from low-resolution spectra. For spectra with signal-to-noise ratios at ɡ band (S/Ng) greater than 10, the model achieves a precision of 85 K for Teff, 0.07 dex for log ɡ, 0.06 dex for [Fe/H], 0.25 mag for MG, and 0.03 mag for (BP – RP)0. The estimated distances have a median fractional error of 4% with a standard deviation of 8%. Results. We applied the trained CNN model to 521 424 solar-like stars to derive the distance and stellar parameters. Compared with other distance estimation studies and spectroscopic surveys, the results show good consistency. Additionally, we investigated the metallicity gradients of the Milky Way from a subsample, and find a radial gradient ranging from −0.05 < Δ[Fe/H]/ΔR < 0.0 dex kpc−1 and a vertical gradient ranging from −0.26 < Δ[Fe/H]/ΔZ < −0.07 dex kpc−1. Conclusions. We conclude that our method is effective in estimating distances and stellar parameters for solar-like stars with limited astrometric data. Our measurements are reliable for Galactic structure studies and hopefully will be useful for exoplanet researches. [ABSTRACT FROM AUTHOR]

This study analyses JWST MIRI/MRS observations of the infrared (IR) polycyclic aromatic hydrocarbon (PAH) bands in the nuclear (∼0.4″ at 11 μm; ∼75 pc) and circumnuclear regions (inner ∼kpc) of local active galactic nuclei (AGNs) from the Galactic Activity, Torus, and Outflow Survey (GATOS). We examine the PAH properties in the circumnuclear regions of AGNs and the projected direction of AGN-outflows and compare them to those in star-forming regions and the innermost regions of AGNs. This study employs 4.9–28.1 μm sub-arcsecond angular resolution data to investigate the properties of PAHs in three nearby sources (DL ∼ 30 − 40 Mpc). Our findings are aligned with previous JWST studies, demonstrating that the central regions of AGNs display a larger fraction of neutral PAH molecules (i.e. elevated 11.3/6.2 and 11.3/7.7 μm PAH ratios) in comparison to star-forming galaxies. We find that AGNs might affect not only the PAH population in the innermost region, but also in the extended regions up to ∼kpc scales. By comparing our observations to PAH diagnostic diagrams, we find that, in general, regions located in the projected direction of the AGN-outflow occupy similar positions on the PAH diagnostic diagrams as those of the innermost regions of AGNs. Star-forming regions that are not affected by the AGNs in these galaxies share the same part of the diagram as star-forming galaxies. We also examined the potential of the PAH-H2 diagram to disentangle AGN-versus-star-forming activity. Our results suggest that in Seyfert-like AGNs, the illumination and feedback from the AGN might affect the PAH population at nuclear and kpc scales, particularly with respect to the ionisation state of the PAH grains. However, PAH molecular sizes are rather similar. The carriers of the ionised PAH bands (6.2 and 7.7 μm) are less resilient than those of neutral PAH bands (11.3 μm), which might be particularly important for strongly AGN-host coupled systems. Therefore, caution must be applied when using PAH bands as star-formation rate indicators in these systems even at kpc scales, with the effects of the AGN being more important for ionised ones. [ABSTRACT FROM AUTHOR]

High-resolution spectrographs open a detailed window onto the atmospheres of stars and planets. As the number of systems observed with different instruments grows, it is crucial to develop a standard in analyzing spectral time series of exoplanet transits and occultations, for the benefit of reproducibility. Here, we introduce the ANTARESS workflow, a set of methods aimed at processing high-resolution spectroscopy datasets in a robust way and extracting accurate exoplanetary and stellar spectra. While a fast preliminary analysis can be run on order-merged 1D spectra and cross-correlation functions (CCFs), the workflow was optimally designed for extracted 2D echelle spectra to remain close to the original detector counts, limit the spectral resampling, and propagate the correlated noise. Input data from multiple instruments and epochs were corrected for relevant environmental and instrumental effects, processed homogeneously, and analyzed independently or jointly. In this first paper, we show how planet-occulted stellar spectra extracted along the transit chord and cleaned from planetary contamination provide a direct comparison with theoretical stellar models and enable a spectral and spatial mapping of the photosphere. We illustrate this application of the workflow to archival ESPRESSO data, using the Rossiter-McLaughlin effect Revolutions (RMR) technique to confirm the spin-orbit alignment of HD 209458b and unveil biases in WASP-76b's published orbital architecture. Because the workflow is modular and its concepts are general, it can support new methods and be extended to additional spectrographs to find a range of applications beyond the proposed scope. In a companion paper, we will present how planet-occulted spectra can be processed further to extract and analyze planetary spectra decontaminated from the star, providing clean and direct measurements of atmospheric properties. [ABSTRACT FROM AUTHOR]

Context. This paper presents the first public data release of the S-PLUS Ultra-Short Survey (USS), a photometric survey with short exposure times, covering approximately 9300 deg2 of the Southern sky. The USS utilizes the Javalambre 12-band magnitude system, including narrow, medium, and broad-band filters targeting prominent stellar spectral features. The primary objective of the USS is to identify bright, extremely metal-poor (EMP; [Fe/H] ≤ −3) and ultra-metal-poor (UMP; [Fe/H] ≤ −4) stars for further analysis using medium- and high-resolution spectroscopy. Aims. This paper provides an overview of the survey observations, calibration method, data quality, and data products. Additionally, it presents the selection of EMP and UMP candidates. Methods. The data from the USS were reduced and calibrated using the same methods as presented in the S-PLUS DR2. An additional step was introduced, accounting for the offset between the observed magnitudes off the USS and the predicted magnitudes from the very low-resolution Gaia XP spectra. Results. This first release contains data for 163 observed fields totaling ~324 deg2 along the Celestial Equator. The magnitudes obtained from the USS are well-calibrated, showing a difference of ~15 mmag compared to the predicted magnitudes by the GaiaXPy toolkit. By combining colors and magnitudes, 140 candidates for EMP or UMP have been identified for follow-up studies. Conclusions. The S-PLUS USS DR1 is an important milestone in the search for bright metal-poor stars, with magnitudes in the range 10 < r ≤ 14. The USS is an ongoing survey; in the near future, it will provide many more bright metal-poor candidate stars for spectroscopic follow-up. [ABSTRACT FROM AUTHOR]

Context. Accurate atmospheric parameters and chemical composition of planet hosts play a major role in characterising exoplanets and understanding their formation and evolution. Aims. Our objective is to uniformly determine atmospheric parameters and chemical abundances of carbon (C), nitrogen (N), oxygen(O), and the α-elements, magnesium (Mg) and silicon (Si), along with C/O, N/O and Mg/Si abundance ratios for planet-hosting stars. In this analysis, we aim to investigate the potential links between stellar chemistry and the presence of planets. Methods. Our study is based on high-resolution spectra of 149 F, G, and K dwarf and giant stars hosting planets or planetary systems. The spectra were obtained with the Vilnius University Echelle Spectrograph (VUES) on the 1.65 m Molėtai Observatory telescope. The determination of stellar parameters was based on a standard analysis using equivalent widths and one-dimensional, plane-parallel model atmospheres calculated under the assumption of local thermodynamical equilibrium. The differential synthetic spectrum method was used to uniformly determine the carbon C(C2), nitrogen N(CN), oxygen [O I], magnesium Mg I, and silicon Si I elemental abundances as well as the C/O, N/O, and Mg/Si ratios. Results. We analysed elemental abundances and ratios in dwarf and giant stars, finding that [C/Fe], [O/Fe], and [Mg/Fe] are lower in metal-rich dwarf hosts; whereas [N/Fe] is close to the Solar ratio. Giants show smaller scatter in [C/Fe] and [O/Fe] and lower than the Solar average [C/Fe] and C/O ratios. The (C+N+O) abundances increase with [Fe/H] in giant stars, with a minimal scatter. We also noted an overabundance of Mg and Si in planet-hosting stars, particularly at lower metallicities, and a lower Mg/Si ratio in stars with planets. In giants hosting high-mass planets, nitrogen shows a moderate positive relationship with planet mass. C/O and N/O ratios show moderate negative and positive slopes in giant stars, respectively. The Mg/Si ratio shows a negative correlation with planet mass across the entire stellar sample. [ABSTRACT FROM AUTHOR]

Bars are expected to impact the distribution of stellar populations both during bar formation, as they rearrange stars into new orbits, and afterwards, due to the redistribution of star-formation-fuelling gas and transfer of angular momentum. We study the impact of stellar bars on the azimuthal variation of stellar population age, metallicity and mass surface density in |$\sim 1\, 000$| nearby barred galaxies from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. Bars have higher stellar mass density (⁠|$0.113^{+0.065}_{-0.067}$|  dex) and are more metal-rich (⁠|$0.028^{+0.033}_{-0.040}$|  dex) than the discs at the same radii. Stellar ages show a variety of bar to interbar contrasts with no consistent trend. The difference in metallicity increases with total stellar mass of the galaxy and distance below the star-forming main sequence. We discuss a combination of potentially responsible processes including kinematic separation, more extended star formation histories and more efficient recycling in bars and at bar-spiral arm connections. Additionally, we observe an offset (⁠|$10^{\circ }$| – |$40^{\circ }$|⁠) of the peak metallicity to the bar major axis in star-forming bars in low-mass galaxies, and more metal-rich regions outside the ends of the bar in long bars and quenched galaxies. Furthermore, there is a subtle trend of lower metallicities on the leading side of spiral arms compared to the trailing side. Finally, we report a spiral arm surface density feature, which could point towards a dominant bar-spiral connection and pitch angle of |$\alpha \sim 25^{\circ }$|⁠. We interpret these features in the context of bar formation and the impact of large-scale gas flows associated with their presence. [ABSTRACT FROM AUTHOR]

Ongoing deep integral-field spectroscopy (IFS) observations of disc galaxies provide opportunities for comparison with the Milky Way (MW) to understand galaxy evolution. However, such comparisons are marred by many challenges such as selection effects, differences in observations and methodology, and proper validation of full-spectrum fitting methods. In this study, we present a novel code GalCraft to address these challenges by generating mock IFS data cubes of the MW using simple stellar population models and a mock MW stellar catalogue derived from E-galaxia. We use the widely adopted full-spectrum fitting code ppxf to investigate the ability to recover kinematics and stellar populations for an edge-on mock MW IFS observation. We confirm that differences in kinematics, mean age, |$[\mathrm{M/H}]$|⁠ , and |$[\mathrm{\alpha /Fe}]$| between thin and thick discs can be distinguished. However, the age distribution is overestimated in the ranges between |$2{-}4$| and |$12{-}14$|  Gyr compared to the expected values. This is likely due to the age spacing and degeneracy of SSP templates. We find systematic offsets in the recovered kinematics due to insufficient spectral resolution and the variation of line-of-sight velocity distribution with age and |$[\mathrm{M/H}]$|⁠. With future higher resolution and multi- |$[\mathrm{\alpha /Fe}]$| simple stellar population templates, GalCraft will be useful to validate key signatures such as |$[\mathrm{\alpha /Fe}]$| – |$[\mathrm{M/H}]$| distribution at different R and |$|z|$| and potentially infer radial migration and kinematic heating efficiency to study detailed chemodynamical evolution of MW-like galaxies. [ABSTRACT FROM AUTHOR]

The radial velocity (RV) method of exoplanet detection requires mitigation of nuisance signals arising from stellar activity. Using analytic cool and facular spot models, we explore the use of central line moments (CLMs) for recovering and monitoring rotation induced RV variability. Different spot distribution patterns, photosphere-spot contrast ratios, and the presence or absence of the convective blueshift lead to differences in CLM signals between M and G dwarfs. Harmonics of the rotation period are often recovered with the highest power in standard periodogram analyses. By contrast, we show the true stellar rotation may be more reliably recovered with string length minimization. For solar minimum activity levels, recovery of the stellar rotation signal from CLMs is found to require unfeasibly high signal-to-noise observations. The stellar rotation period can be recovered at solar maximum activity levels from CLMs for reasonable cross-correlation function (CCF) signal-to-noise ratios >1000–5000. The CLMs can be used to recover and monitor stellar activity through their mutual correlations and correlations with RV and bisector inverse span. The skewness of a CCF, a measure of asymmetry, is described by the third CLM, |$M_3$|⁠. Our noise-free simulations indicate the linear RV versus |$M_3$| correlation is up to 10 per cent higher than the RV versus bisector inverse span correlation. We find a corresponding ∼5 per cent increase in linear correlation for CARMENES observations of the M star, AU Mic. We also assess the effectiveness of the time derivative of the second CLM, |$M_2$|⁠ , for monitoring stellar activity. [ABSTRACT FROM AUTHOR]

The Wide Angle Search for Planets (WASP) survey used transit photometry to discover nearly 200 gas-giant exoplanets and derive their planetary and stellar parameters. Reliable determination of the planetary density depends on accurate measurement of the planet's radius, obtained from the transit depth and photodynamical determination of the stellar radius. The stellar density and hence the stellar radius are typically determined in a model-independent way from the star's reflex orbital acceleration and the transit profile. Additional flux coming from the system due to a bright, undetected stellar binary companion can, however, potentially dilute the transit curve and radial velocity signal, leading to underestimation of the planet's mass and radius, and to overestimation of the planet's density. In this study, we cross-check the published radii of all the WASP planet-host stars, determined from their transit profiles and radial velocity curves, against radiometric measurements of stellar radii derived from their angular diameters (via the infrared flux method) and trigonometric parallaxes. We identify eight systems showing radiometric stellar radii significantly greater than their published photodynamical values: WASPs 20, 85, 86, 103, 105, 129, 144, and 171. We investigate these systems in more detail to establish plausible ranges of angular and radial velocity separations within which such 'stealth binaries' could evade detection, and deduce their likely orbital periods, mass ratios, and flux ratios. After accounting for the dilution of transit depth and radial velocity amplitude, we find that, on average, the planetary densities for the identified stealth binary systems should be reduced by a factor of 1.3. [ABSTRACT FROM AUTHOR]

In the realm of astronomical spectroscopic observation, the purity of skylight spectra is crucial for accurate analysis, often complicated by interference from neighboring celestial objects. Addressing this challenge, a novel automatic purification algorithm is proposed in this study, leveraging the power of auto-coding mechanisms. By harnessing the inherent data features and shared representations between skylight and target objects, this method effectively isolates skylight spectra from residual signals of neighboring objects. Central to this approach is the utilization of an encoder-decoder framework. The encoder dynamically learns the combined features of skylight and target objects, generating respective coding vectors. These vectors are then utilized to subtract the target-specific features from the skylight coding space, facilitating the extraction of pure skylight characteristics. Subsequently, the decoder reconstructs the refined skylight data, effectively eliminating residual components associated with neighboring celestial bodies. A notable strength of this algorithm lies in its ability to perform feature extraction and purification autonomously, without relying on labeled data. Experimental validation conducted on LAMOST-DR5 datasets demonstrates the efficacy of the proposed method. By effectively removing spectral information from target objects within skylight spectra, the algorithm yields comparatively pure skylight spectra, paving the way for enhanced astronomical spectroscopic analyses. [ABSTRACT FROM AUTHOR]

Under the assumption of hierarchical galaxy formation, dwarf galaxies are the closest existing analogues to the high-redshift protogalaxies that merged to form the Milky Way. These low-mass systems serve as unique laboratories for studying nucleosynthetic channels given that the chemical compositions of their stars play a pivotal role in constraining their chemical enrichment history. To date, stellar abundances in dwarf galaxies have focused almost exclusively on elemental abundance ratios. While important, elemental abundances omit critical information about the isotopic composition. Here, we compute the Mg isotopic ratios of six accreted dwarf galaxy stars (low |$\alpha$|⁠) and seven Milky Way stars (high |$\alpha$|⁠) using a set of high-resolution (65 000 < R < 160 000) and high signal-to-noise ratio (⁠|$\rm {S/N} \gt 250$|⁠) optical spectra. We show, for the first time, that at a given [Fe/H] stars born in a dwarf galaxy differ in their Mg isotopic ratios from stars born in the Milky Way. However, when comparing isotopic ratios at a given [Mg/H] rather than [Fe/H], a powerful diagnostic emerges that suggests nucleosynthesis processes are consistent across different stellar environments. This universality of Mg isotopic abundances provides additional dimensionality for chemical evolution models and helps to constrain massive star nucleosynthesis across cosmic time. [ABSTRACT FROM AUTHOR]

Brown dwarfs and planetary-mass companions display rotationally modulated photometric variability, especially those near the L/T transition. This variability is commonly attributed to top-of-atmosphere (TOA) inhomogeneities, with proposed models including patchy thick and thin clouds, planetary-scale jets, or chemical disequilibrium. Surface mapping techniques are powerful tools to probe their atmospheric structures and distinguish between models. One of the most successful methods for stellar surface mapping is Doppler imaging, where the existence of TOA inhomogeneities can be inferred from their varying Doppler shifts across the face of a rotating star. We applied Doppler imaging to the nearest brown dwarf binary WISE 1049AB (also known as Luhman 16AB) using time-resolved, high-resolution spectroscopic observations from Gemini IGRINS, and obtained for the first time H - and K -band simultaneous global weather map for brown dwarfs. Compared to the only previous Doppler map for a brown dwarf in 2014 featuring a predominant mid-latitude cold spot on WISE 1049B and no feature on WISE 1049A, our observations detected persistent spot-like structures on WISE 1049B in the equatorial to mid-latitude regions on two nights, and revealed new polar spots on WISE 1049A. Our results suggest stability of atmospheric features over time-scale of days and possible long-term stable or recurring structures. H - and K -band maps displayed similar structures in and out of CO bands, indicating the cold spots not solely due to chemical hotspots but must involve clouds. Upcoming 30-m extremely large telescopes will enable more sensitive Doppler imaging of dozens of brown dwarfs and even a small number of directly imaged exoplanets. [ABSTRACT FROM AUTHOR]

Context. When retrieving exoplanet atmospheric characteristics from spectroscopic observations, parameter estimation results strongly depend on the chosen forward model. In the era of the James Webb Space Telescope (JWST) and other next-generation facilities, the increased signal-to-noise ratio (S/N), wavelength coverage, and spectral resolution of observations warrant closer investigations into factors that could inadvertently bias the results of these retrievals. Aims. We aim to investigate the impact of utilising multi-point pressure–temperature (p–T) profiles of varying complexity on the retrieval of synthetically generated hot-Jupiter transmission spectra modelled after state-of-the-art observations of the hot Jupiter WASP-39 b with JWST. Methods. We performed homogenised atmospheric retrievals with the TauREx retrieval framework on a sample of synthetically generated transmission spectra, accounting for varying cases of underlying p–T profiles, cloud-top pressures, and expected noise levels. These retrievals are performed using a fixed-pressure multi-point p–T prescription with increasing complexity, ranging from isothermal to an eleven-point profile. We evaluated the performance of the retrievals based on the Bayesian model evidence, and the accuracy of the retrievals was compared to the known input parameters. Results. We find that performing atmospheric retrievals using an isothermal prescription for the pressure–temperature profile consistently results in wrongly retrieved atmospheric parameters when compared to the known input parameters. For an underlying p–T profile with a fully positive lapse rate, we find that a two-point profile is sufficient to retrieve the known atmospheric parameters, while under the presence of an atmospheric temperature inversion, we find that a more complex profile is necessary. Conclusions. Our investigation shows that, for a data quality scenario mirroring state-of-the-art observations of a hot Jupiter with JWST, an isothermal p–T prescription is insufficient to correctly retrieve the known atmospheric parameters. We find a model complexity preference dependent on the underlying pressure–temperature structure, but we argue that a p–T prescription on the complexity level of a four-point profile should be preferred. This represents the overlap between the lowest number of free parameters and the highest model preference in the cases investigated in this work. [ABSTRACT FROM AUTHOR]

Context. Most known spectroscopic binaries are detected through the variation in the radial velocity of the primary star, while the spectral features of the secondary companion remain hidden in the noise. Aims. We present a novel technique for the spectroscopic detection of low-luminosity secondary companions of binary stars. The main goal is to estimate the mass ratio even when the radial velocity of the secondary cannot be measured in individual spectra. Methods. The method aims to bring together all the spectral information of the secondary component into one single feature. In a first step, a spectral disentangling technique is used in an automatic way for a grid of possible values of the mass ratio. Then, the resulting series of secondary component spectra are compared with a grid of synthetic templates with a technique inspired by spectral cross-correlations. By optimizing a function indicative of the significance of the secondary detection, the mass ratio and an estimate of effective temperature are derived. Results. We apply our method to different types of objects and observational datasets: three single-lined spectroscopic binaries in the open cluster Blanco 1 observed at mid-spectral resolution, an early-type binary in the open cluster NGC 2362, and PX Vir, an F-type binary observed at high resolution for which the secondary companion had been detected in the infrared but not in the optical spectral range. It is shown that from standard-quality spectral datasets it is possible to detect the secondary star in systems in which the secondary contributes less than 0.5–1.0% of the total flux. [ABSTRACT FROM AUTHOR]

Context. Ultra-luminous X-ray sources (ULXs) are high-mass X-ray binaries with an X-ray luminosity above 1039 erg s−1. These ULXs can be powered by black holes that are more massive than 20 M⊙, accreting in a standard regime, or lighter compact objects accreting supercritically. There are only a few ULXs with known optical or ultraviolet (UV) counterparts, and their nature is debated. Determining whether optical/UV radiation is produced by the donor star or by the accretion disc is crucial for understanding ULX physics and testing massive binary evolution. Aims. We conduct, for the first time, a fully consistent multi-wavelength spectral analysis of a ULX and its circumstellar nebula. We aim to establish the donor star type and test the presence of strong disc winds in the prototypical ULX Holmberg II X-1 (Ho II X-1). Furthermore, we aim to obtain a realistic spectral energy distribution of the ionising source, which is needed for robust nebula analysis. We acquired new UV spectra of Ho II X-1 with the Hubble Space Telescope (HST) and complemented them with archival optical and X-ray data. We explored the spectral energy distribution of the source and analysed the spectra using the stellar atmosphere code PoWR and the photoionisation code CLOUDY. Our analysis of the X-ray, UV, and optical spectra of Ho II X-1 and its nebula consistently explains the observations. We do not find traces of disc wind signatures in the UV and the optical, rejecting previous claims of the ULX being a supercritical accretor. The optical/UV counterpart of Ho II X-1 is explained by a B-type supergiant donor star. Thus, the observations are fully compatible with Ho II X-1 being a close binary consisting of an ≳66 M⊙ black hole accreting matter from an ≃22 M⊙ B-supergiant companion. Furthermore, we propose a possible evolution scenario for the system, suggesting that Ho II X-1 is a potential gravitational wave source progenitor. [ABSTRACT FROM AUTHOR]

Context. ESPRESSO guaranteed time observations (GTOs) at the 8.2m VLT telescope were performed to look for Earth-like exoplanets in the habitable zone of nearby stars. Barnard's star is a primary target within the ESPRESSO GTO as it is the second closest neighbour to our Sun after the α Centauri stellar system. Aims. We present here a large set of 156 ESPRESSO observations of Barnard's star carried out over four years with the goal of exploring periods of shorter than 50 days, thus including the habitable zone (HZ). Methods. Our analysis of ESPRESSO data using Gaussian process (GP) to model stellar activity suggests a long-term activity cycle at 3200 d and confirms stellar activity due to rotation at 140 d as the dominant source of radial velocity (RV) variations. These results are in agreement with findings based on publicly available HARPS, HARPS-N, and CARMENES data. ESPRESSO RVs do not support the existence of the previously reported candidate planet at 233 d. Results. After subtracting the GP model, ESPRESSO RVs reveal several short-period candidate planet signals at periods of 3.15 d, 4.12 d, 2.34 d, and 6.74 d. We confirm the 3.15 d signal as a sub-Earth mass planet, with a semi-amplitude of 55 ± 7 cm s−1, leading to a planet minimum mass mp sin i of 0.37 ± 0.05 M⊕, which is about three times the mass of Mars. ESPRESSO RVs suggest the possible existence of a candidate system with four sub-Earth mass planets in circular orbits with semi-amplitudes from 20 to 47 cm s−1, thus corresponding to minimum masses in the range of 0.17–0.32 M⊕. Conclusions. The sub-Earth mass planet at 3.1533 ± 0.0006 d is in a close-to circular orbit with a semi-major axis of 0.0229 ± 0.0003 AU, thus located inwards from the HZ of Barnard's star, with an equilibrium temperature of 400 K. Additional ESPRESSO observations would be required to confirm that the other three candidate signals originate from a compact short-period planet system orbiting Barnard's star inwards from its HZ. [ABSTRACT FROM AUTHOR]

Motivated by the observed ~30% variations in flux from the L7 dwarf VHS 1256 b, we subjected its time-resolved Hubble Space Telescope (HST) WFC3 spectra (measured in two epochs: 2018 and 2020), as well as medium-resolution Very Large Telescope (VLT) X-shooter and Early Release Science James Webb Space Telescope (JWST) spectra to a suite of both standard Bayesian (nested sampling) and machine-learning (random forest) retrievals. We find that both HST and VLT data require vertically varying abundance profiles of water in order to model the spectra accurately. Despite the large flux variations observed in the HST data, the temporal variability cannot be attributed to a single varying atmospheric property. The retrieved atmospheric quantities are consistent with being invariant across time. However, we find that model grids offer relatively poor fits to the measured HST spectra and are unsuitable for quantifying the temporal variability of atmospheric properties. Additionally, our analysis of JWST spectra using model grids indicates consistency in terms of the retrieved properties across different wavelength channels. Despite the temporal variability in flux, the retrieved properties between HST and VLT, as well those as between HST and JWST, are consistent within the respective posterior uncertainties. Such an outcome bodes well for future retrieval analyses of exoplanetary atmospheres, which are expected to exhibit weaker flux variations. [ABSTRACT FROM AUTHOR]

Context. Neutron-capture elements represent an important nucleosynthetic channel in the study of the Galactic chemical evolution of stellar populations. For stellar populations behind significant extinction, such as those in the Galactic centre and along the Galactic plane, abundance analyses based on near-infrared (NIR) spectra are necessary. Previously, spectral lines from the neutron-capture elements, such as copper (Cu), cerium (Ce), neodymium (Nd), and ytterbium (Yb), have been identified in the H band, while yttrium (Y) lines have been identified in the K band. Aims. Due to the scarcity of spectral lines from neutron-capture elements in the NIR, the addition of useful spectral lines from other neutron-capture elements is highly desirable. The aim of this work is to identify and characterise a spectral line suitable for abundance determination from the most commonly used s-process element, namely barium. Methods. We observed the NIR spectra of 37 M giants in the solar neighbourhood at high spectral resolution and with a high signal-to-noise ratio using the IGRINS spectrometer on the GEMINI South telescope. The full H- and K-bands were recorded simultaneously at R = 45 000. Using a manual spectral synthesis method, we determined the fundamental stellar parameters for these stars and derived the barium abundance from the Ba line (6s5d 3D2 → 6s6p 3P2o) at λair = 23 253.56 Å in the K band. Results. We demonstrate that the Ba line in the K band at 2.33 μm (λ23 253.56) is useful for abundance analyses from the spectra of M giants. The line becomes progressively weaker at higher temperatures and is only useful in M giants and the coolest K giants at supersolar metallicities. Conclusions. We can now add Ba to the trends of the heavy elements Cu, Zn, Y, Ce, Nd, and Yb, which can be retrieved from high-resolution H- and K-band spectra. This opens up the study of nucleosynthetic channels, including the s-process and the r-process, in dust-obscured populations. Thus, these elements can be studied for heavily dust-obscured regions of the Galaxy, such as the Galactic centre. [ABSTRACT FROM AUTHOR]

We present a high-resolution chemical study of a representative sample of 21 luminous giant stars in Liller 1, a complex stellar system in the Galactic bulge, based on H-band spectra acquired with the Near-Infrared Spectrograph at KeckII. In this sample, we found fifteen stars with a subsolar iron abundance and enhanced [α/Fe] and [Al/Fe], likely older, having formed early and quickly from gas mainly enriched by type II supernovae, and six stars with supersolar iron and roughly solar-scaled [α/Fe] and [Al/Fe], likely younger, having formed at later epochs from gas also enriched by type Ia supernovae. Moreover, both subpopulations show enhanced [N/Fe], as in the bulge field, approximately solar-scaled [V/Fe], and depletion of [C/Fe] and 12C/13C with respect to the solar values, indicating the occurrence of significant mixing in the stellar interiors of these evolved stars. Our study also reveals that the subsolar subpopulation shows some structuring, and the presence of a third subcomponent with iron content and intermediate [α/Fe] enhancement, in between that of the metal-poor and metal-rich main subpopulations, has been statistically assessed, providing the chemical signature of both an extended star formation with multiple bursts and some self-enrichment. [ABSTRACT FROM AUTHOR]

CXOU J110926.4−650224 is a candidate transitional millisecond pulsar (tMSP) with X-ray and radio emission properties reminiscent of those observed in confirmed tMSPs in their X-ray 'subluminous' disc state. We present the results of observing campaigns that, for the first time, characterise the optical and near-infrared variability of this source and establish a connection with the mode-switching phenomenon observed in X-rays. The optical emission exhibited flickering activity, frequent dipping episodes where it appeared redder, and a multi-peaked flare where it was bluer. The variability pattern was strongly correlated with that of the X-ray emission. Each dip matched an X-ray low-mode episode, indicating that a significant portion of the optical emission originates from nearly the same region as the X-ray emission. The near-infrared emission also displayed remarkable variability, including a dip of 20 min in length during which it nearly vanished. Time-resolved optical spectroscopic observations reveal significant changes in the properties of emission lines from the disc and help infer the spectral type of the companion star to be between K0 and K5. We compare the properties of CXOU J110926.4−650224 with those of other tMSPs in the X-ray subluminous disc state and discuss our findings within the context of a recently proposed scenario that explains the phenomenology exhibited by the prototypical tMSP PSR J1023+0038. [ABSTRACT FROM AUTHOR]

The planetary system K2-24 is composed of two transiting low-density Neptunians locked in an almost perfect 2:1 resonance and showing large transit time variations (TTVs), and it is an excellent laboratory to search for signatures of planetary migration. Previous studies performed with K2, Spitzer, and RV data tentatively claimed a significant non-zero eccentricity for one or both planets, possibly high enough to challenge the scenario of pure disk migration through resonant capture. With 13 new CHEOPS light curves (seven of planet b, six of planet c), we carried out a global photometric and dynamical re-analysis by including all the available literature data as well. We obtained the most accurate set of planetary parameters to date for the K2-24 system, including radii and masses at 1% and 5% precision (now essentially limited by the uncertainty on stellar parameters) and non-zero eccentricities eb = 0.0498−0.0018+0.0011, ec = 0.0282−0.0007+0.0003 detected at very high significance for both planets. Such relatively large values imply the need for an additional physical mechanism of eccentricity excitation during or after the migration stage. Also, while the accuracy of the previous TTV model had drifted by up to 0.5 days at the current time, we constrained the orbital solution firmly enough to predict the forthcoming transits for the next ~15 years, thus enabling efficient follow-up with top-level facilities such as JWST or ESPRESSO. [ABSTRACT FROM AUTHOR]

Context. HD 209458 b is one of the most studied exoplanets to date. Despite this, atmospheric characterisation studies yielded inconsistent species detections and abundances. Values reported for the C/O ratio range from ≈0.1 to 1.0. Of particular interest is the simultaneous detection of H2O and HCN reported by some studies using high-resolution ground-based observations, which would require the atmospheric C/O ratio to be fine-tuned to a narrow interval around 1. HCN has however not been detected from recent space-based observations. Aims. We aim to provide an independent study of HD 209458 b's atmosphere with high-resolution observations, in order to infer the presence of several species, including H2O and HCN. Methods. We observed four primary transits of HD 209458 b at a high resolution (ℛ ≈ 92000) with CRIRES+ in the near infrared (band H, 1.431243–1.837253 μm). After reducing the data with pycrires, we prepared the data using the SysRem algorithm and performed a cross-correlation (CCF) analysis of the transmission spectra. We also compared the results with those obtained from simulated datasets constructed by combining the Exo-REM self-consistent model with the petitRADTRANS package. Results. Combining the four transits, we detect H2O with a signal-to-noise CCF metric of 8.7σ. This corresponds to a signal emitted at Kp = 151.3−23.4+31.1 km s−1 and blueshifted by −6−2+1 km s−1, consistent with what is expected for HD 209458 b. We do not detect any other species among C2H2, CH4, CO, CO2, H2S, HCN, and NH3. Comparing this with our simulated datasets, this result is consistent with a C/O ratio of 0.1 and an opaque cloud top pressure of 50 Pa, at a 3 times solar metallicity. This would also be consistent with recent JWST observations. However, none of the simulated results obtained with a bulk C/O ratio of 0.8, a value suggested by previous studies using GIANO-B and CRIRES, are consistent with our observations. [ABSTRACT FROM AUTHOR]

Context. The nature of the close-in rocky planet 55 Cnce is puzzling, despite it having been observed extensively. Its optical and infrared occultation depths show temporal variability, in addition to a phase curve variability observed in the optical. Aims. We wish to explore the possibility that the variability originates from the planet being in a 3:2 spin–orbit resonance, and thus showing different sides during occultations. We proposed and were awarded Cycle 1 time at the James Webb Space Telescope (JWST) to test this hypothesis. Methods. JWST/NIRCam (Near Infrared Camera) observed five occultations (secondary eclipses) of the planet – of which four were observed within a week – simultaneously at 2.1 and 4.5 µm. While the former gives band-integrated photometry, the latter provides a spectrum between 3.9–5.0 µm. Results. We find that the occultation depths in both bandpasses are highly variable and change between a non-detection (−5 ± 6 ppm and 7 ± 9 ppm) to 96 ± 8 ppm and 119−19+34 ppm at 2.1 µm and 4.5 µm, respectively. Interestingly, the variations in both bandpasses are not correlated and do not support the 3:2 spin-orbit resonance explanation. The measured brightness temperature at 4.5 µm varies between 873–2256 K and is lower than the expected day-side temperature of bare rock with no heat redistribution (2500 K), which is indicative of an atmosphere. Our atmospheric retrieval analysis of occultation depth spectra at 4.5 µm finds that different visits statistically favour various atmospheric scenarios including a thin outgassed CO/CO2 atmosphere and a silicate rock vapour atmosphere. Some visits even support a flat line model. Conclusions. The observed variability could be explained by stochastic outgassing of CO/CO2, which is also hinted at by retrievals. Alternatively, the variability observed at both 2.1 and 4.5 µm could be the result of a circumstellar patchy dust torus generated by volcanism on the planet. [ABSTRACT FROM AUTHOR]

Aims. Obtaining accurate derivations of stellar atmospheric parameters is crucial in the fields of stellar and exoplanet characterization. We present the upgraded version of our computational tool ODUSSEAS with a new reference scale applied to derive Teff and [Fe/H] values for M dwarfs. Methods. The new reference dataset of ODUSSEAS consists of Teff values based on interferometry, and [Fe/H] values derived by applying updated values for the parallaxes. These reference parameters are related to the pseudo-equivalent widths (EWs) of more than 4000 stellar absorption lines. The machine learning Python "scikit learn" package creates models to determine the stellar parameters for subsequent analysis. Results. We determined Teff and [Fe/H] values for 82 planet-host stars in SWEET-Cat. We demonstrate that our new version of ODUSSEAS is capable of determining the parameters with a greater accuracy than the original by comparing our results to other methods in literature. We also compared our parameters for the same stars by measuring their spectra obtained from several instruments, showing the consistency of our determinations with standard deviation of 30 K and 0.03 dex. Finally, we examined the correlation among planetary mass and stellar metallicity, confirming prior evidence indicating that massive planets mainly form around metal-rich stars in the case of M dwarfs as well. [ABSTRACT FROM AUTHOR]

Context. The study of exoplanets at different evolutionary stages can shed light on their formation, migration, and evolution. The determination of exoplanet properties depends on the properties of their host stars. It is therefore important to characterise the host stars for accurate knowledge on their planets. Aims. Our final goal is to derive, in a homogeneous and accurate way, the stellar atmospheric parameters and elemental abundances of ten young TESS (Transiting Exoplanet Survey Satellite) transiting planet-hosting GK stars followed up with the HARPS-N (High Accuracy Radial velocity Planet Searcher for the Northern hemisphere) at TNG (Telescopio Nazionale Galileo) spectrograph within the Global Architecture of Planetary Systems (GAPS) programme. Methods. We derived stellar kinematic properties, atmospheric parameters, and abundances of 18 elements. Depending on stellar parameters and chemical elements, we used methods based on line equivalent widths and spectral synthesis. Lithium line measurements were used as approximate age estimations. We exploited chemical abundances and their ratios to derive information on planetary composition. Results. Elemental abundances and kinematic properties are consistent with the nearby Galactic thin disk. All targets show C/O<0.8 and 1.0

By using high-resolution spectra acquired with FLAMES-GIRAFFE at the ESO/VLT, we measured the radial and rotational velocities of 115 stars in the Galactic globular cluster M 55. After field decontamination based on the radial velocity values, the final sample of member stars is composed of 32 blue straggler stars (BSSs) and 76 reference stars populating the red giant and horizontal branches of the cluster. In agreement with previous findings, the totality of red giant branch stars has negligible rotation (<10 km s−1) and horizontal branch stars have rotational velocities of 40 km s−1 at most. In contrast, the BSS rotational velocity distribution shows a long tail extending up to ~200 km s−1, with 15 BSSs (out of 32), spinning faster than 40 km s−1. By defining the threshold for fast rotating BSSs at 40 km s−1, this sets the percentage of these stars at 47 ±14%. Such a large value has never been found before in any globular clusters. It is roughly comparable to that measured in other loose systems (ω Centauri, M 4, and NGC 3201) and significantly larger than that observed in high-density clusters (as 47 Tucanae, NGC 6397, NGC 6752, and M 30). This evidence supports a scenario whereby recent BSS formation is occurring in low-density environments. We also find that the BSS rotational velocity tends to decrease for decreasing luminosity, as found for another loose cluster of the sample, namely, NGC 3201. [ABSTRACT FROM AUTHOR]

Context. The possibility of observing spectral features in exoplanet atmospheres with space missions like the James Webb Space Telescope (JWST) and Atmospheric Remote-sensing Infrared Exoplanet Large-survey (ARIEL) necessitates the accurate modelling of cloud particle opacities. In exoplanet atmospheres, cloud particles can be made from multiple materials and be considerably chemically heterogeneous. Therefore, assumptions on the morphology of cloud particles are required to calculate their opacities. Aims. The aim of this work is to analyse how different approaches to calculate the opacities of heterogeneous cloud particles affect the optical properties of cloud particles and how this may influence the interpretation of data observed by JWST and future missions. Methods. We calculated cloud particle optical properties using seven different mixing treatments: four effective medium theories (EMTs; Bruggeman, Landau-Lifshitz-Looyenga (LLL), Maxwell-Garnett, and Linear), core-shell, and two homogeneous cloud particle approximations. We conducted a parameter study using two-component materials to study the mixing behaviour of 21 commonly considered cloud particle materials for exoplanets. To analyse the impact on observations, we studied the transmission spectra of HATS-6b, WASP-39b, WASP-76b, and WASP-107b. Results. Materials with large refractive indices, like iron-bearing species or carbon, can change the optical properties of cloud particles when they comprise less than 1% of the total particle volume. The mixing treatment of heterogeneous cloud particles also has an observable effect on transmission spectroscopy. Assuming core-shell or homogeneous cloud particles results in less muting of molecular features and retains the cloud spectral features of the individual cloud particle materials. The predicted transit depths for core-shell and homogeneous cloud particle materials are similar for all planets used in this work. If EMTs are used, cloud spectral features are broader and the cloud spectral features of the individual cloud particle materials are not retained. Using LLL leads to fewer molecular features in transmission spectra than when using Bruggeman. [ABSTRACT FROM AUTHOR]

Context. In modern Galactic astronomy, stellar spectroscopy plays a pivotal role in complementing large photometric and astrometric surveys and enabling deeper insights to be gained into the chemical evolution and chemo-dynamical mechanisms at play in the Milky Way and its satellites. Nonetheless, the use of different instruments and dedicated pipelines in various spectroscopic surveys can lead to differences in the derived spectroscopic parameters. Aims. Efforts to homogenise these surveys onto a common scale are essential to maximising their scientific legacy. To this aim, we developed the SPECTROTRANSLATOR, a data-driven deep neural network algorithm that converts spectroscopic parameters from the base of one survey (base A) to that of another (base B). Methods. SPECTROTRANSLATOR is comprised of two neural networks: an intrinsic network, where all the parameters play a role in computing the transformation, and an extrinsic network, where the outcome for one of the parameters depends on all the others, but not the reverse. The algorithm also includes a method to estimate the importance that the various parameters play in the conversion from base A to B. Results. To demonstrate the workings of the algorithm, we applied it to transform effective temperature, surface gravity, metallicity, [Mg/Fe], and line-of-sight velocity from the base of GALAH DR3 into the APOGEE-2 DR 17 base. We demonstrate the efficiency of the SPECTROTRANSLATOR algorithm to translate the spectroscopic parameters from one base to another, directly using parameters by the survey teams. We were able to achieve a similar performance than previous works that have performed a similar type of conversion but using the full spectrum, rather than the spectroscopic parameters. This allowed us to reduce the computational time and use the output of pipelines optimised for each survey. By combining the transformed GALAH catalogue with the APOGEE-2 catalogue, we studied the distribution of [Fe/H] and [Mg/Fe] across the Galaxy and we found that the median distribution of both quantities present a vertical asymmetry at large radii. We attribute it to the recent perturbations generated by the passage of a dwarf galaxy across the disc or by the infall of the Large Magellanic Cloud. Conclusions. Several aspects still need to be refined, such as the question of the optimal way to deal with regions of the parameter space meagrely populated by stars in the training sample. However, SPECTROTRANSLATOR has already demonstrated its capability and is poised to play a crucial role in standardising various spectroscopic surveys onto a unified framework. [ABSTRACT FROM AUTHOR]

Context. Close white dwarf binaries (CWDBs) are considered to be progenitors of several exotic astronomical phenomena (e.g., type Ia supernovae, cataclysmic variables). These violent events are broadly used in studies of general relativity and cosmology. However, obtaining precise stellar parameter measurements for both components of CWDBs is a challenging task given their low luminosities, swift time variation, and complex orbits. High-resolution spectra (R > 20 000) are preferred but expensive, resulting in a sample size that is insufficient for robust population study. Recently, studies have shown that the more accessible low-resolution (R ~ 2000) spectra (LRS) may also provide enough information for spectral decomposition. To release the full potential of the less expensive low-resolution spectroscopic surveys, and thus greatly expand the CWDB sample size, it is necessary to develop a robust pipeline for spectra decomposition and analysis. Aims. We aim to develop a spectroscopic fitting program for white dwarf binary systems based on photometry, LRS, and stellar evolutionary models. The outputs include stellar parameters of both companions in the binary including effective temperature, surface gravity, mass, radius, and metallicity in the case of MS stars. Methods. We used an artificial neural network (ANN) to build spectrum generators for DA/DB white dwarfs and main-sequence stars. Characteristic spectral lines were used to decompose the spectrum of each component. The best-fit stellar parameters were obtained by finding the least χ2 solution to these feature lines and the continuum simultaneously. Compared to previous studies, our code is innovative in the following aspects: (1) implementing a sophisticated binary decomposition technique in LRS for the first time; (2) using flux-calibrated spectra instead of photometry plus spectral lines, in which the latter requires multi-epoch observations; (3) applying an ANN in binary decomposition, which significantly improves the efficiency and accuracy of generated spectra. Results. We demonstrate the reliability of our code with two well-studied CWDBs, WD 1534+503 and PG 1224+309. We also estimate the stellar parameters of 14 newly identified CWDB candidates, most of which are fitted with double component models for the first time. Our estimates agree with previous results for the common stars and follow the statistical distribution in the literature. Conclusions. We provide a robust program for fitting binary spectra of various resolutions. Its application to a large volume of white dwarf binary candidates will offer important statistic samples to stellar evolution studies and future gravitational wave monitoring. [ABSTRACT FROM AUTHOR]

Context. Stellar ages are an important parameter in studies of the chemical evolution of the Galaxy. To better estimate these ages, various methods complementary to the conventional isochrone fitting method have been implemented in the past decade. Several recent studies have established the existence of a relationship between chemical clocks and stellar ages. The [Y/Mg] clock is a promising technique, but there are still several open questions, such as its validity for metal-poor stars and differences between the thin and thick disk populations. Aims. Our aim is to study the relationship between the [Y/Mg] chemical clock and stellar ages for a sample of solar-type disk stars and to provide the empirical dating relation(s) for the stellar age determination from their precise chemical abundances. We also studied the effect of metallicity and populations on this chemical clock. Methods. We derived precise stellar atmospheric parameters as well as the elemental abundances of Mg and Y through line-by-line differential spectroscopic analysis for a sample of 48 metal-poor solar-type stars based on high-quality, high-resolution ESO/HARPS spectra. From high-precision Gaia astrometric data, stellar masses and ages were estimated through isochrone fitting using Yonsei-Yale isochrones. A joint analysis of our sample, together with a sample of 185 solar twins and analogues from our previous works, was performed to calibrate the [Y/Mg] chemical clock in the Galactic disk for −0.71 < [Fe/H] < +0.34. Open clusters and stars with asteroseismic ages were used to validate our relations. Results. Two different populations are clearly seen in the [Mg/Fe]−[Fe/H] plane: the thick and thin disks. Thick disk stars show an age-metallicity relation, whereas the thin disk shows a flatter age–metallicity distribution. We find a strong, metallicity–dependent anti-correlation between the [Y/Mg] ratio and the stellar ages of our sample. For the first time in the literature, we report similar correlations for thin and thick disk stars. Conclusions. We find that the [Y/Mg] relation(s) found here for solar-type stars in a wide metallicity range are compatible with those found for solar twins in the literature. Our relation provides high accuracy and precision (0.45 and 0.99 Gyr, respectively) comparable with the best accuracy achieved for solar twins to date. [ABSTRACT FROM AUTHOR]

Context. Gamma-ray bursts are the most energetic known explosions. Although they fade rapidly, they give us the opportunity to measure redshift and important properties of their host galaxies. We report the photometric and spectroscopic study of the Swift GRB 160203A at z = 3.518, and its host galaxy. Fine-structure absorption lines, detected in the afterglow at different epochs, allow us to investigate variability due to the strong fading background source. Aims. We obtained two optical to near-infrared spectra of the GRB afterglow with X-shooter on ESO/VLT, 18 minutes and 5.7 hours after the burst, allowing us to investigate temporal changes of fine-structure absorption lines. Methods. We measured H I column density log N(HI/cm–2) = 21.75 ± 0.10, and several heavy-element ions along the GRB sightline in the host galaxy, among which Si II, Al II, Al III, C II, Ni II, Si IV, C IV, Zn II and Fe II, and Fe II∗ and Si II∗ fine-structure transitions from energetic levels excited by the afterglow, at the common redshift z = 3.518. We measured [M/H]TOT = –0.78 ± 0.13 and a [Zn/Fe]FIT = 0.69 ± 0.15, representing the total (dust corrected) metallicity and dust depletion, respectively. We detected additional intervening systems along the line of sight at ɀ = 1.03, ɀ = 1.26, ɀ = 1.98, ɀ = 1.99, ɀ = 2.20, and ɀ = 2.83. We could not measure significant variability in the strength of the fine-structure lines throughout all the observations and determined an upper limit for the GRB distance from the absorber of d < 300 pc, adopting the canonical UV pumping scenario. However, we note that the quality of our data is not sufficient to conclusively rule out collisions as an alternative mechanism. Results. GRB 160203A belongs to a growing sample of GRBs with medium resolution spectroscopy, provided by the Swift/X-shooter legacy programme, which enables a detailed investigation of the interstellar medium in high-redshift GRB host galaxies. In particular, this host galaxy shows relatively high metal enrichment and dust depletion already in place when the universe was only 1.8 Gyr old. [ABSTRACT FROM AUTHOR]

Understanding the relationship between quenching mechanisms that transform star-forming galaxies into quiescent ones and galaxy properties remains a challenge. We investigate the gas and stellar properties of 69 double-peaked galaxies selected from the Sloan Digital Sky Survey (SDSS) and observed as part of the Mapping Nearby Galaxies at APO (MaNGA) survey to elucidate the mechanisms driving star formation quenching within these systems. We study their star formation activity along with their physical properties: colour, morphology, environment, stellar age, and gas ionisation diagnostics. We find that these 69 double-peaked MaNGA galaxies encompass a higher fraction of galaxies in the green valley, based on the corrected NUV − r colour, compared to our defined control samples of single-peaked emission line galaxies. This green colour traces intermediate stellar populations compared to blue and red galaxies, as indicated by the Dn(4000) index. These green galaxies show no recent star formation bursts within the last 2 Gyr. They exhibit emission line ratios that are suggestive of both ongoing star formation and nuclear activity. They are predominantly located in isolated or small group environments, indicating that internal processes rather than external factors drive their quenching. Moreover, optical emission lines detected throughout a significant area of these systems suggest that gas depletion is unlikely to be the primary quenching mechanism. These findings support a scenario where quenching is instead caused by reduced star formation efficiency. [ABSTRACT FROM AUTHOR]

We combine stellar orbits with the abundances of the heavy, r -process element europium and the light, |$\alpha$| -element, silicon to separate in situ and accreted populations in the Milky Way (MW) across all metallicities. At high orbital energy, the accretion-dominated halo shows elevated values of [Eu/Si], while at lower energies, where many of the stars were born in situ , the levels of [Eu/Si] are lower. These systematically different levels of [Eu/Si] in the MW and the accreted halo imply that the scatter in [Eu/ |$\alpha$| ] within a single galaxy is smaller than previously thought. At the lowest metallicities, we find that both accreted and in situ populations trend down in [Eu/Si], consistent with enrichment via neutron star mergers. Through compiling a large data set of abundances for 54 globular clusters (GCs), we show that differences in [Eu/Si] extend to populations of in situ /accreted GCs. We interpret this consistency as evidence that in r -process elements GCs trace the star formation history of their hosts, motivating their use as sub-Gyr timers of galactic evolution. Furthermore, fitting the trends in [Eu/Si] using a simple galactic chemical evolution model, we find that differences in [Eu/Si] between accreted and in situ MW field stars cannot be explained through star formation efficiency alone. Finally, we show that the use of [Eu/Si] as a chemical tag between GCs and their host galaxies extends beyond the Local Group, to the halo of M31 – potentially offering the opportunity to do Galactic Archaeology in an external galaxy. [ABSTRACT FROM AUTHOR]

In this work, we enhance the FNet , a 1D convolutional neural network (CNN) with a residual neural network (ResNet) architecture, to perform spectral classification of quasars, galaxies, stars, and broad absorption line (BAL)-quasars in the SDSS-IV catalogue from DR17 of eBOSS. Leveraging its convolutional layers and the ResNet structure with different kernel sizes, FNet autonomously identifies various patterns within the entire sample of spectra. Since FNet does not require the intermediate step of identifying specific lines, a simple modification enabled our current network to classify all SDSS spectra. This modification involves changing the final output layer from a single value (redshift) to multiple values (probabilities of all classes), and accordingly adjusting the loss function from mean squared error to cross-entropy. FNet achieves a completeness of 99.00  per cent |$\pm$| 0.20 for galaxies, 98.50  per cent |$\pm$| 0.30 for quasars, 99.00  per cent |$\pm$| 0.18 for BAL-quasars, and 98.80 per cent |$\pm$| 0.20 for stars. These results are comparable to those obtained using QuasarNET , a standard CNN employed in the SDSS routine, comprises convolutional layers without the ResNet structure with equal kernel sizes, and is utilized for redshift measurement and classification by identifying seven emission lines. QuasarNET , in order to overcome the problem of finding a C  iv emission line with broad absorption which is slightly more challenging than that of detecting emission lines requires to add BAL C  iv line to the list of lines that the network learns to identify. However, this procedure is not necessary in FNet as it learns the features through a self-learning procedure. [ABSTRACT FROM AUTHOR]

We present results on simultaneous observations of Class I methanol masers at 25, 36, and 44 GHz towards 22 Galactic targets carried out with the Effelsberg 100-m telescope. The study investigates relations between the hyperfine (HF) structure of the torsion–rotation transitions in CH |$_3$| OH and maser activity. By analysing the radial velocity shifts between different maser lines together with the patterns of the HF structure based on laboratory measurements and quantum-chemical calculations, we find that in any source only one specific HF transition forms the maser emission and that this transition changes from source to source. The physical conditions leading to this selective behaviour are still unclear. Using accurate laboratory rest frequencies for the 25 GHz transitions, we have refined the centre frequencies for the HF multiplets at 36, 44, and 95 GHz: |$f_{\scriptscriptstyle 36} = (36169.2488\pm 0.0002_{\scriptscriptstyle \rm stat} \pm 0.0004_{\scriptscriptstyle \rm sys})$|  MHz. |$f_{\scriptscriptstyle 44} = (44069.4176\pm 0.0002_{\scriptscriptstyle \rm stat} \pm 0.0004_{\scriptscriptstyle \rm sys})$|  MHz, and |$f_{\scriptscriptstyle 95} = (95169.4414\pm 0.0003_{\scriptscriptstyle \rm stat} \pm 0.0004_{\scriptscriptstyle \rm sys})$|  MHz. Comparison with previous observations of 44 GHz masers performed 6–10 yr ago with a Korean 21-m Korean Very Long Baseline Interferometry Network telescope towards the same targets confirms the kinematic stability of Class I maser line profiles during this time interval and reveals a systematic radial velocity shift of |$0.013\pm 0.005$|  km s |$^{-1}$| between the two telescopes. [ABSTRACT FROM AUTHOR]

The recent detection of ethanolamine (EtA, HOCH |$_2$| CH |$_2$| NH |$_2$|⁠), a key component of phospholipids, i.e. the building blocks of cell membranes, in the interstellar medium is in line with an exogenous origin of life-relevant molecules. However, the stability and survivability of EtA molecules under inter/circumstellar and Solar System conditions have yet to be demonstrated. Starting from the assumption that EtA mainly forms on interstellar ice grains, we have systematically exposed EtA, pure and mixed with amorphous water (H |$_2$| O) ice, to electron, ion, and thermal processing, representing 'energetic' mechanisms that are known to induce physicochemical changes within the ice material under controlled laboratory conditions. Using infrared (IR) spectroscopy, we have found that heating of pure EtA ice causes a phase change from amorphous to crystalline at 180 K, and further temperature increase of the ice results in sublimation-induced losses until full desorption occurs at about 225 K. IR and vacuum ultraviolet (VUV) spectra of EtA-containing ices deposited and irradiated at 20 K with 1 keV electrons as well as IR spectra of H |$_2$| O:EtA mixed ice obtained after 1 MeV He |$^+$| ion irradiation have been collected at different doses. The main radiolysis products, including H |$_2$| O, CO, CO |$_2$|⁠ , NH |$_3$|⁠ , and CH |$_3$| OH, have been identified and their formation pathways are discussed. The measured column density of EtA is demonstrated to undergo exponential decay upon electron and ion bombardment. The half-life doses for electron and He |$^+$| ion irradiation of pure EtA and H |$_2$| O:EtA mixed ice are derived to range between |$10.8\!-\!26.3$|  eV/16u. Extrapolating these results to space conditions, we conclude that EtA mixed in H |$_2$| O ice is more stable than in pure form and it should survive throughout the star and planet formation process. [ABSTRACT FROM AUTHOR]