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Context. The light element (anti-)correlations shown by globular clusters (GCs) are the main spectroscopic signature of multiple stellar populations. These internal abundance variations provide us with fundamental constraints on the formation mechanism of stellar clusters. Aims. Using Gaia-ESO, the largest and most homogeneous survey of open clusters (OCs), we intend to check whether these stellar aggregates display the same patterns. Based on previous studies of many GCs, several young and massive clusters in the Magellanic Clouds, as well as a few OCs, we do not expect to find any anti-correlation, given the low mass of Milky Way OCs. Methods. We used the results based on UVES spectra of stars in Gaia-ESO to derive the distribution of Na and O abundances and see whether they show an unexplained dispersion or whether they are anti-correlated. By selecting only high-probability members with high-precision stellar parameters, we ended up with more than 700 stars in 74 OCs. We examined the O-Na distribution in 28 OCs with at least 4 stars available as well as the Na distribution in 24 OCs, with at least 10 stars available. Results. We find that the distribution of Na abundances is compatible with a single-value population, within the errors. The few apparent exceptions can be explained by differences in the evolutionary phase (main sequence and giant post first dredge-up episode) or by difficulties in analysing low gravity giants. We did not find any indication of an Na-O anti-correlation in any of the clusters for which O has been derived. Conclusions. Based on the very small spread we find, OCs maintain the status of single stellar populations. However, a definitive answer requires studying more elements and larger samples covering different evolutionary phases. This will be possible with the next generation of large surveys. [ABSTRACT FROM AUTHOR]

A density functional theory study was performed to understand the interactions of a small Ti 4 cluster with multi-vacancy graphene. We also consider the effect produced by the B-doping of the vacancy defect. In this sense, we analyze the binding mechanisms of the metal cluster. The focus is set on its stability on the substrate, geometrical structure and the interactions participating between the cluster and graphene substrate. A qualitative study of the principal bonds was carried out employing overlap population and bond order chemical descriptors. Additionally, as an attempt to comprehend better the electronic structure and related properties, we performed total density of states, band structure and magnetic moment calculations to characterize the electrical and magnetic properties of the B-doped and non-doped systems. [ABSTRACT FROM AUTHOR]

Context. Young open clusters (ages of less than 200 Myr) have been observed to exhibit several peculiarities in their chemical compositions. These anomalies include a slightly sub-solar iron content, super-solar abundances of some atomic species (e.g. ionised chromium), and atypical enhancements of [Ba/Fe], with values up to ~0.7 dex. Regarding the behaviour of the other s-process elements like yttrium, zirconium, lanthanum, and cerium, there is general disagreement in the literature: some authors claim that they follow the same trend as barium, while others find solar abundances at all ages. Aims. In this work we expand upon our previous analysis of a sample of five young open clusters (IC 2391, IC 2602, IC 4665, NGC 2516, and NGC 2547) and one star-forming region (NGC 2264), with the aim of determining abundances of different neutron-capture elements, mainly Cu I, Sr I, Sr II, Y II, Zr II, Ba II, La II, and Ce II. For NGC 2264 and NGC 2547 we present the measurements of these elements for the first time. Methods. We analysed high-resolution, high signal-to-noise spectra of 23 solar-type stars observed within the Gaia-ESO survey. After a careful selection, we derived abundances of isolated and clean lines via spectral synthesis computations and in a strictly differential way with respect to the Sun. Results. We find that our clusters have solar [Cu/Fe] within the uncertainties, while we confirm that [Ba/Fe] is super-solar, with values ranging from +0.22 to +0.64 dex. Our analysis also points to a mild enhancement of Y, with [Y/Fe] ratios covering values between 0 and +0.3 dex. For the other s-process elements we find that [X/Fe] ratios are solar at all ages. Conclusions. It is not possible to reconcile the anomalous behaviour of Ba and Y at young ages with standard stellar yields and Galactic chemical evolution model predictions. We explore different possible scenarios related to the behaviour of spectral lines, from the dependence on the different ionisation stages and the sensitivity to the presence of magnetic fields (through the Landé factor) to the first ionisation potential effect. We also investigate the possibility that they may arise from alterations of the structure of the stellar photosphere due to the increased levels of stellar activity that affect the spectral line formation, and consequently the derived abundances. These effects seem to be stronger in stars at ages of less than ~ 100 Myr. However, we are still unable to explain these enhancements, and the Ba puzzle remains unsolved. With the present study we suggest that other elements, for example Sr, Zr, La, and Ce, might be more reliable tracer of the s-process at young ages, and we strongly encourage further critical observations. [ABSTRACT FROM AUTHOR]

Hydrogen adsorption stability, geometry, electronic structure and mechanism has been investigated on Ni 4 cluster embedded in graphene with three, four and six vacancies by density functional theory (DFT) calculations. An energetic analysis of hydrogen adsorption by addition of one to four H 2 molecules was performed for each system in order to determine their hydrogen storage capacity. Dispersion force contribution to the adsorption energy is quantitative evaluated to know whether H 2 molecules adsorption behavior is dominated by chemical or van der Waals interactions. A further analysis of this type of interactions is also addressed by total and partial density of states. Bonding and charge transfer characteristics for the different steps involved in the adsorption mechanism are also included. Special attention is given to the effects caused by this new Ni/graphene interface to the hydrogen adsorption behavior. Image 1 • Hydrogen adsorption on Ni 4 embedded in multivacancy defected graphene was studied. • Three adsorption mechanism were identified. • First molecule adsorbed can be dissociated. • Up to four hydrogen molecules can be adsorbed with physicochemical interaction. [ABSTRACT FROM AUTHOR]

The determination of the fundamental properties (mass, separation, age, gravity, and atmospheric properties) of brown dwarf companions allows us to infer crucial informations on their formation and evolution mechanisms. Spectroscopy of substellar companions is available to date only for a limited number of objects (and mostly at very low resolution, R  < 50) because of technical limitations, i.e. contrast and angular resolution. We present medium resolution (R  = 350), coronagraphic long-slit spectroscopic observations with SPHERE of two substellar companions, HD 1160 B and HD 19467 B. We found that HD 1160 B has a peculiar spectrum that cannot be fitted by spectra in current spectral libraries. A good fit is possible only considering separately the Y + J and the H spectral band. The spectral type is between M5 and M7. We also estimated a T eff of 2800–2900 K and a log  g of 3.5–4.0 dex. The low surface gravity seems to favour young age (10–20 Myr) and low mass (∼20 MJup ) for this object. HD 19467 B is instead a fully evolved object with a T eff of ∼1000 K and log  g of ∼5.0 dex. Its spectral type is T6 ± 1. [ABSTRACT FROM AUTHOR]

NiTi alloy has important properties such as shape-memory, super-plasticity, resistance, and biocompatibility, therefore is frequently used in biomedical devices. We studied the oxidized form of this alloy and possible Ni segregation in three possible models for the TiO 2 /NiTi interface: i) the perfect interface; ii) the Ni enriched interface and iii) with oxygen vacancies in the TiO 2 coating. We used DFT + U calculations for TiO 2 , because Hubbard correction encourages localization of the excess electronic charge and improves the DFT results. A standard spin polarized DFT was used for NiTi. We obtained the optimized geometries for each model and computed segregation energy, electronic structure, magnetic moment and bond order for the interface and for Ni segregation. Our calculations indicated that Ti3+ species are present at the interface, while in the bulk of the oxide layer the species is the Ti4+. Also, the electronic structure show that the metallic character of the alloy is unaffected by the interaction with oxygen. These results are consistent with experimental data from literature. Ni enriched interface containing O vacancies show a strong geometric distortion in the TiO 2 layers. In all cases, Ni segregation is an a thermodynamically unfavorable process, helping to understand the biocompatibility of NiTi alloy. Unlabelled Image • Ni segregation is an unfavorable process in all considered models. • A Ni-rich interface with oxygen vacancies is the less unfavorable situation for segregation. • Bond order analysis indicates an important Ni O bonding at the perfect interface. • The first layer of TiO2 on NiTi produces a relevant blocking effect in Ni segregation. • The introduction of oxygen vacancies induces a strong distortion in the oxide layers regularity. [ABSTRACT FROM AUTHOR]

Methanol adsorption on PtCo(111) surface at low coverage is studied using Density Functional Theory (DFT) calculations without and with van der Waals corrections. We investigated the PtCo FCT alloy surface with a uniform distribution. The most favorable site for CH 3 OH adsorption is on top of a Co atom, with an adsorption energy of −0.92 eV. Methanol attachs to the surface by the O atom, with a distance of 2.24 Å. The molecule presents a small distortion after adsorption. The C O Co bond angle is 142°. The C H bonds are strengthened whereas the C O and O H bonds are weakened. A charge transfer from C atom to O atom occurs upon adsorption, and then further transfer occurs to the Co atom on the surface. The calculated vibrational frequencies for adsorbed methanol present a red-shift displacement compared to gas-phase, confirming the adsorption process. [ABSTRACT FROM AUTHOR]

An ab initio dynamics study was performed with the aim of understanding better the hydrogen adsorption mechanism, stability and capacity with the temperature on Ni 4 cluster embedded in a three vacancy graphene substrate. Additionally, the hydrogen migration to the substrate was analyzed observing an outstanding improvement for the activation energy compared with the systems without vacancies. Moreover, a suitable reduction in the hydrogen migration energy barriers was achieved with the subsequent hydrogen adsorption of more molecules on the cluster. Consequently, in the light of these new insights hydrogen spillover on Ni 4 can be highly influenced by both, vacancy defects and the saturation with hydrogen molecules. [Display omitted] • Hydrogen adsorption on Ni 4 embedded in three vacancy defected graphene is studied. • AIMD and NEB calculations were performed. • Adsorbed hydrogen stability with temperature on a Ni 4 cluster is analyzed. • Defect effect on the energy barrier reduction for H migration process is showed. • The favoring of H spillover by Ni cluster H 2 saturation was determined. [ABSTRACT FROM AUTHOR]

The presence of multiple populations in globular clusters has been well established thanks to high-resolution spectroscopy. It is widely accepted that distinct populations are a consequence of different stellar generations: intracluster pollution episodes are required to produce the peculiar chemistry observed in almost all clusters. Unfortunately, the progenitors responsible have left an ambiguous signature and their nature remains unresolved. To constrain the candidate polluters, we have measured lithium and aluminium abundances in more than 180 giants across three systems: NGC 1904, NGC 2808, and NGC 362. The present investigation along with our previous analysis of M12 and M5 affords us the largest data base of simultaneous determinations of Li and Al abundances. Our results indicate that Li production has occurred in each of the three clusters. In NGC 362, we detected an M12-like behaviour, with first- and second-generation stars sharing very similar Li abundances favouring a progenitor that is able to produce Li, such as asymptotic giant branches stars. Multiple progenitor types are possible in NGC 1904 and NGC 2808, as they possess both an intermediate population comparable in lithium to the first generation stars and also an extreme population, that is enriched in Al but depleted in Li. A simple dilution model fails in reproducing this complex pattern. Finally, the internal Li variation seems to suggest that the production efficiency of this element is a function of the cluster's mass and metallicity - low-mass or relatively metal-rich clusters are more adept at producing Li. [ABSTRACT FROM AUTHOR]

Formic acid adsorption on CaO (001) is analyzed using Density Functional Theory (DFT) with Van der Waals corrections, implemented through the Vienna ab Initio Simulation Package (VASP). Our calculations reveals two possible adsorption sites at low coverage with adsorption energies of − 2. 38 eV and − 2. 07 eV. For both sites we found a similar structural behavior, with a considerable elongation of the formic acid O H bond with respect to the molecular distance. The analysis of the electronic structure and bonding show a stabilization of formic acid as a result of a shift in their states to lower energies, with respect to the gas phase. There is a small charge transfer (0. 03 e − ) from the hydrogen to the surface. At the same time, formic acid oxygens also experiment a charge decrease of 0. 15 e − and 0. 13 e − , being the ones with the greatest charge variation during the adsorption process. [Display omitted] • Formic acid adsorbs on CaO (001) in two possible configurations. • The bond with the surface is developed mainly through formic acid hydrogen. • The most affected bond in the adsorption process is the O H of the HCOOH. • There is charge transfer from formic acid to the surface in the adsorption process. [ABSTRACT FROM AUTHOR]

Highlights: [•] The most favorable site is a HCP site for benzene and CO top on Pt for the co-adsorption (−1.62eV). [•] CCO O tilt angles are similar both considered cases (4°5′ and 3°23′). [•] The more developed OP is Pt CCO. [•] A very small H CCO interaction is detected. Also, small Pt H and Co CCO OP are found. [•] The calculated vibrational frequencies show a red shift compared to gas-phase. [ABSTRACT FROM AUTHOR]

We explore the possible connection between the open cluster IC 2391 and the unbound Argus association identified by the search for associations containing young stars survey. In addition to common kinematics and ages between these two systems, here we explore their chemical abundance patterns to confirm if the two substructures shared a common origin. We carry out a homogenous high-resolution elemental abundance study of eight confirmed members of IC 2391 as well as six members of the Argus association using UVES spectra. We derive spectroscopic stellar parameters and abundances for Fe, Na, Mg, Al, Si, Ca, Ti, Cr, Ni and Ba.All stars in the open cluster and Argus association were found to share similar abundances with the scatter well within the uncertainties, where [Fe/H] = −0.04 ± 0.03 for cluster stars and [Fe/H] = −0.06 ± 0.05 for Argus stars. Effects of overionization/excitation were seen for stars cooler than roughly 5200 K as previously noted in the literature. Also, enhanced Ba abundances of around 0.6 dex were observed in both systems. The common ages, kinematics and chemical abundances strongly support the fact that the Argus association stars originated from the open cluster IC 2391. Simple modelling of this system finds this dissolution to be consistent with two-body interactions. [ABSTRACT FROM AUTHOR]

ABSTRACT We present stellar parameters and abundances of 11 elements (Li, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni and Zn) of 13 F6-K2 main-sequence stars in the young groups AB Doradus, Carina Near and Ursa Major. The exoplanet-host star ι Horologii is also analysed. The three young associations have lithium abundance consistent with their age. All other elements show solar abundances. The three groups are characterized by a small scatter in all abundances, with mean [Fe/H] values of 0.10 (σ = 0.03), 0.08 (σ = 0.05) and 0.01 (σ = 0.03) dex for AB Doradus, Carina Near and Ursa Major, respectively. The distribution of elemental abundances appears congruent with the chemical pattern of the Galactic thin disc in the solar vicinity, as found for other young groups. This means that the metallicity distribution of nearby young stars, targets of direct-imaging planet-search surveys, is different from that of old, field solar-type stars, i.e. the typical targets of radial velocity surveys. The young planet-host star ι Horologii shows a lithium abundance lower than that found for the young association members. It is found to have a slightly super-solar iron abundance ([Fe/H] = 0.16 ± 0.09), while all [X/Fe] ratios are similar to the solar values. Its elemental abundances are close to those of the Hyades cluster derived from the literature, which seems to reinforce the idea of a possible common origin with the primordial cluster. [ABSTRACT FROM AUTHOR]

We studied the distribution of aluminum abundances among red giants in the peculiar globular cluster NGC 1851. Aluminum abundances were derived from the strong doublet Al i 8772-8773 Å measured on intermediate-resolution FLAMES spectra of 50 cluster stars acquired under the Gaia-ESO public survey. We coupled these abundances with previously derived abundances of O, Na, and Mg to fully characterize the interplay of the NeNa and MgAl cycles of H-burning at high temperature in the early stellar generation in NGC 1851. The stars in our sample show well-defined correlations between Al, Na and Si; Al is anticorrelated with O and Mg. The average value of the [Al/Fe] ratio steadily increases from the first generation stars to the second generation populations with intermediate and extremely modified composition. We confirm on a larger database the results recently obtained by us: the pattern of abundances of proton-capture elements implies a moderate production of Al in NGC 1851. We find evidence of a statistically significant positive correlation between Al and Ba abundances in the more metal-rich component of red giants in NGC 1851. [ABSTRACT FROM AUTHOR]

We studied the distribution of aluminum abundances among red giants in the peculiar globular cluster NGC 1851. Aluminum abundances were derived from the strong doublet Al I 8772-8773 Å measured on intermediate-resolution FLAMES spectra of 50 cluster stars acquired under the Gaia-ESO public survey. We coupled these abundances with previously derived abundances of O, Na, and Mg to fully characterize the interplay of the NeNa and MgAl cycles of H-burning at high temperature in the early stellar generation in NGC 1851. The stars in our sample show well-defined correlations between Al, Na and Si; Al is anticorrelated with O and Mg. The average value of the [Al/Fe] ratio steadily increases from the first generation stars to the second generation populations with intermediate and extremely modified composition. We confirm on a larger database the results recently obtained by us: the pattern of abundances of proton-capture elements implies a moderate production of Al in NGC 1851. We find evidence of a statistically significant positive correlation between Al and Ba abundances in the more metal-rich component of red giants in NGC 1851. [ABSTRACT FROM AUTHOR]

ABSTRACT Recently, several studies have shown that young, open clusters are characterized by a considerable overabundance in their barium content. In particular, D'Orazi et al. reported that in some younger clusters [Ba/Fe] can reach values as high as ∼0.6 dex. The work also identified the presence of an anticorrelation between [Ba/Fe] and cluster age. For clusters in the age range ∼4.5 Gyr -500 Myr, this is best explained by assuming a higher contribution from low-mass asymptotic giant branch stars to the Galactic chemical enrichment. The purpose of this work is to investigate the ubiquity of the barium overabundance in young stellar clusters. We analysed high-resolution spectroscopic data, focusing on the s-process elemental abundance for three nearby young associations, i.e. AB Doradus, Carina-Near and Ursa Major. The clusters have been chosen such that their age spread would complement the D'Orazi et al. study. We find that while the s-process elements Y, Zr, La and Ce exhibit solar ratios in all three associations, Ba is overabundant by ∼0.2 dex. Current theoretical models cannot reproduce this abundance pattern; thus, we investigate whether this unusually large Ba content might be related to chromospheric effects. Although no correlation between [Ba/Fe] and several activity indicators seems to be present, we conclude that different effects could be at work which may (directly or indirectly) be related to the presence of hot stellar chromospheres. [ABSTRACT FROM AUTHOR]

Recently, several studies have shown that young, open clusters are characterized by a considerable overabundance in their barium content. In particular, D’Orazi et al. reported that in some younger clusters [Ba/Fe] can reach values as high as ∼0.6 dex. The work also identified the presence of an anticorrelation between [Ba/Fe] and cluster age. For clusters in the age range ∼4.5 Gyr-500 Myr, this is best explained by assuming a higher contribution from low-mass asymptotic giant branch stars to the Galactic chemical enrichment.The purpose of this work is to investigate the ubiquity of the barium overabundance in young stellar clusters. We analysed high-resolution spectroscopic data, focusing on the s-process elemental abundance for three nearby young associations, i.e. AB Doradus, Carina-Near and Ursa Major. The clusters have been chosen such that their age spread would complement the D’Orazi et al. study.We find that while the s-process elements Y, Zr, La and Ce exhibit solar ratios in all three associations, Ba is overabundant by ∼0.2 dex. Current theoretical models cannot reproduce this abundance pattern; thus, we investigate whether this unusually large Ba content might be related to chromospheric effects. Although no correlation between [Ba/Fe] and several activity indicators seems to be present, we conclude that different effects could be at work which may (directly or indirectly) be related to the presence of hot stellar chromospheres. [ABSTRACT FROM AUTHOR]

We have obtained medium- and low-resolution spectroscopy and BVI CCD imaging of Berkeley 32, an old open cluster which lies in the anticentre direction. From the radial velocities of 48 stars in the cluster direction, we found that 31 of them, in crucial evolutionary phases, are probable cluster members, with an average radial velocity of . From isochrone fitting to the colour–magnitude diagrams of Berkeley 32, we have obtained an age of and . The best fit is obtained with . A consistent distance, , has been derived from the mean magnitude of red clump stars with confirmed membership; we may assume . The colour–magnitude diagram of the nearby field observed to check for field stars contamination looks intriguingly similar to that of the Canis Major overdensity. [ABSTRACT FROM AUTHOR]

• Pt-decorated defected carbon nanotubes show very favorable COS adsorption energies. • Bonding order analysis suggests COS chemisorption mainly through C and S atoms. • Charge density shows a significant electronic transfer from surface to COS molecule. • Density of states confirms the strong interaction between COS and Pt-doped nanotube. Carbonyl sulfide (COS) is a dangerous gas produced from fossil fuel combustion and petrochemical procedures, so proper adsorbent and sensors are required for removal and detection. In this work, we study by Density Functional Theory methods the COS adsorption on a Pt-decorated vacancy-defected carbon nanotube, in order to evaluate the potential of this nanostructure as gas adsorbent or sensing material. First, we analyze the most stable configuration for Pt adsorption on the defective nanotube, obtaining a more favorable binding energy for a symmetric structure with equivalent C Pt bonds. Next, several configurations are studied for COS adsorption on the Pt-doped nanotube. In the most stable systems, the adsorbate interacts with the Pt decoration through its C and S atoms, with adsorption energy values of about −2.7 eV. Overlap population and bonding order studies are also performed, showing a strong affinity between COS and the Pt-doped surface. Furthermore, an important electronic transfer from nanotube to the gas molecule was detected, which would indicate chemical adsorption. Density of states analysis also show a considerable stabilization of COS molecule after adsorption. Our study suggests that a Pt-doped carbon surface could act as a promising adsorbent and chemical sensor for COS gas removal or detection purposes. [ABSTRACT FROM AUTHOR]

In the present study, we performed density functional theory (DFT) calculations in order to study the structure and stability of small Ni clusters embedded in graphene multivacancy systems. The Bader charges, band structure, total density of states, partial density of states (PDOS), and spin density magnetization were obtained to understand the effects of the cluster size on the electronic and magnetic properties, and thus to determine their potential applications in spintronic devices. Ni cluster adsorption, modified graphene multivacancy substrate behavior, and conversion from a conductor to a semiconductor could be achieved when the cluster size was changed. A linear dispersion relationship around the reciprocal point K was conserved for most of the systems with the inclusion of a band gap between the Dirac cones, which is important for obtaining semiconductors with massless fermions. Comparisons with Ni clusters adsorbed in pristine graphene showed that combining vacancy defects with Ni allows higher band gaps to be obtained. We also analyzed the interactions between Ni clusters and vacancy defects based on the PDOS results. Ni clusters with different sizes could generate ferromagnetic and ferrimagnetic couplings with graphene that exhibited three, four, and six (D 2h and D 6h symmetry) vacancies. The generation of ferromagnetism when Ni 3 and Ni 4 absorbed in graphene (with four and six vacancies, respectively) demonstrates both ferromagnetic and semiconductor behaviors can be obtained, thereby making them good candidates for use as dilute magnetic semiconductors. Ni clusters did not magnetize or exhibit slight magnetization on pristine graphene, and the ferromagnetic coupling was only achieved after the introduction of vacancy defects. • Ni n structures embedded in multivacancy graphene studied using DFT. • Conductor to semiconductor conversion observed as Ni cluster size varied. • Multivacancy defects increased charge transfer from Ni clusters to graphene. • Ferromagnetic, ferrimagnetic, and nonmagnetic behavior observed. • Absorbed Ni 3 and Ni 4 clusters could be applied as dilute magnetic semiconductors. [ABSTRACT FROM AUTHOR]

• The more favorable adsorption sites for are on one (or two) Ca cations. • C2H5OH-surface distance is in the range of 2.3–2.5 Å; with E ads is −1.12 (−1.14) eV. • The adsorbed O H group is 53% (51%) larger that its molecular distance. • Distances and BO are similar for Ca O molecule and Ca O surface. • Charge transfer occurs from O atom (2nd layer) to Ca ions (1st layer). Ethanol adsorption on CaO (0 0 1) surface at low coverage is studied using Density Functional Theory (DFT) calculations with van der Waals corrections. We investigated the CaO surface in its rock salt structure. The more favorable sites for C 2 H 5 OH adsorption are on one (or two) Ca cations bonding the O atom from ethanol, while H atom bond to surface oxygens with an adsorption energy of −1.12 (−1.14) eV. The distance of ethanol to surface is in the range of 2.3–2.5 Å. The molecule presents a strong elongation of the adsorbed O H group being 53% (51%) larger that its molecular distance. Bond order analysis shows that distances and BO are similar for Ca O molecule and Ca O surface. A charge transfer occurs from O atom of the 2nd layer to Ca ions at 1st layer and the molecular O atom gain some charge, while H loses charge towards surface oxygen and from this to the rest of the surface. [ABSTRACT FROM AUTHOR]

Context. The formation mechanisms of stellar, brown dwarf, and planetary companions, their dependencies on the environment and their interactions with each other are still not well established. Recently, combining high-contrast imaging and space astrometry we found that Jupiter-like (JL) planets are frequent in the β Pic moving group (BPMG) around those stars where their orbit can be stable, prompting further analysis and discussion. Aims. We broaden our previous analysis to other young nearby associations to determine the frequency, mass and separation of companions in general and JL in particular and their dependencies on the mass and age of the associations. Methods. We collected available data about companions to the stars in the BPMG and seven additional young associations, including those revealed by visual observations, eclipses, spectroscopy and astrometry. Results. We determined search completeness and found that it is very high for stellar companions, while completeness corrections are still large for JL companions. Once these corrections are included, we found a high frequency of companions, both stellar (>0.52 ± 0.03) and JL (0.57 ± 0.11). The two populations are clearly separated by a gap that corresponds to the well-known brown dwarf desert. Within the population of massive companions, we found clear trends in frequency, separation, and mass ratios with stellar mass. Planetary companions pile up in the region just outside the ice line and we found them to be frequent once completeness was considered. The frequency of JL planets decreases with the overall mass and possibly the age of the association. Conclusions. We tentatively identify the two populations as due to disk fragmentation and core accretion, respectively. The distributions of stellar companions with a semi-major axis <1000 au is indeed well reproduced by a simple model of formation by disk fragmentation. The observed trends with stellar mass can be explained by a shorter but much more intense phase of accretion onto the disk of massive stars and by a more steady and prolonged accretion on solar-type stars. Possible explanations for the trends in the population of JL planets with association mass and age are briefly discussed. [ABSTRACT FROM AUTHOR]

We performed density functional calculation of the acetylene hydrogenation reaction on the PdGa(110) surface. The reaction C 2 H 2 +H 2 → C 2 H 4 is modeled and understood in terms of chemical bonding change. The evolution of electronic structure and electron density plot also shed more light on the role of Pd, Ga and C 2 H 2 during the hydrogenation reactions. This new way of looking at a particular chemical reaction includes the changes in bond order in the different reaction steps. As mentioned before the role of Ga is revealed as a part of the active site and not a single spacer. [ABSTRACT FROM AUTHOR]

Atmospheric mass loss plays a major role in the evolution of exoplanets. This process is driven by the stellar high-energy irradiation, especially in the first hundreds of millions of years after dissipation of the proto-planetary disk. A major source of uncertainty in modeling atmospheric photoevaporation and photochemistry is due to the lack of direct measurements of the stellar flux at extreme-UV (EUV) wavelengths. Several empirical relationships have been proposed in the past to link EUV fluxes to emission levels in X-rays, but the stellar samples employed for this aim are heterogeneous, and the available scaling laws provide significantly different predictions, especially for very active stars. We present new far-UV and X-ray observations of V1298 Tau with Hubble Space Telescope/Cosmic Origins Spectrograph and XMM-Newton, aimed to determine more accurately the high-energy emission of this solar-mass pre-main-sequence star, which hosts four exoplanets. Spectroscopic data were employed to derive the plasma emission measure distribution versus temperature, from the chromosphere to the corona, and the possible variability of this irradiation on short and year-long timescales, due to magnetic activity. As a side result, we have also measured the chemical abundances of several elements in the outer atmosphere of V1298 Tau. We employ our results as a new benchmark point for the calibration of the X-ray to EUV scaling laws, and hence to predict the time evolution of the irradiation in the EUV band, and its effect on the evaporation of exo-atmospheres. [ABSTRACT FROM AUTHOR]

We characterize twelve young stellar objects (YSOs) located in the Lupus I region, spatially overlapping with the Upper Centaurus Lupus (UCL) sub-stellar association. The aim of this study is to understand whether the Lupus I cloud has more members than what has been claimed so far in the literature and gain a deeper insight into the global properties of the region. We selected our targets using the Gaia DR2 catalog based on their consistent kinematic properties with the Lupus I bona fide members. In our sample of twelve YSOs observed by X-shooter, we identified ten Lupus I members. We could not determine the membership status of two of our targets, namely Gaia DR2 6014269268967059840 and 2MASS J15361110-3444473 due to technical issues. We found out that four of our targets are accretors, among them, 2MASS J15551027-3455045, with a mass of ∼0.03 M⊙, is one of the least massive accretors in the Lupus complex identified to date. Several of our targets (including accretors) are formed in situ and off-cloud with respect to the main filaments of Lupus I; hence, our study may hint that there are diffused populations of M dwarfs around Lupus I main filaments. In this context, we would like to emphasize that our kinematic analysis with Gaia catalogs played a key role in identifying the new members of the Lupus I cloud. [ABSTRACT FROM AUTHOR]

Stellar models provide a vital basis for many aspects of astronomy and astro-physics. Recent advances in observational astronomy - through asteroseismology, precision photometry, high-resolution spectroscopy, and large-scale surveys - are placing stellar models under greater quantitative scrutiny than ever. The model limitations are being exposed and the next generation of stellar models is needed as soon as possible. The current uncertainties in the models propagate to the later phases of stellar evolution, hindering our understanding of stellar populations and chemical evolution. Here we give a brief overview of the evolution, importance, and substantial uncertainties of core helium burning stars in particular and then briefly discuss a range of methods, both theoretical and observational, that we are using to advance the modelling. [ABSTRACT FROM AUTHOR]

Using photometry and high-resolution spectroscopy we investigate for the first time the physical connection between the open clusters NGC 5611 and Trumpler 22. Based on new CCD photometry we report their spatial proximity and common age of ~70 Myr. Based on highresolution spectra collected using the HERMES and UCLES spectrographs on the Anglo- Australian telescope' we present radial velocities and abundances for Fe' Na' Mg' Al' Si' Ca, and Ni. The measured radial velocities are -38.63 ± 2.25 km s-1 for NGC 5611 and -38.46 ± 2.08 km s-1 for Trumpler 22. The mean metallicity of NGC 5611 was found to be [Fe/H] = - 0.18 ± 0.02 and for Trumpler 22 was found to be [Fe/H] = -0.17 ± 0.04. The two clusters share similar abundances across the other elements' indicative of a common chemical enrichment history of these clusters. Together with common motions and ages we confirm that NGC 5611 and Trumpler 22 are a primordial binary cluster pair in the Milky Way. [ABSTRACT FROM AUTHOR]

Using photometry and high-resolution spectroscopy we investigate for the first time the physical connection between the open clusters NGC 5617 and Trumpler 22. Based on new CCD photometry we report their spatial proximity and common age of ~70 Myr. Based on highresolution spectra collected using the HERMES and UCLES spectrographs on the Anglo- Australian telescope, we present radial velocities and abundances for Fe, Na, Mg, Al, Si, Ca, and Ni. The measured radial velocities are -38.63 ± 2.25 km s-1 for NGC 5617 and -38.46 ± 2.08 km s-1 for Trumpler 22. The mean metallicity of NGC 5617 was found to be [Fe/H]=-0.18 ± 0.02 and for Trumpler 22 was found to be [Fe/H]=-0.17 ± 0.04. The two clusters share similar abundances across the other elements, indicative of a common chemical enrichment history of these clusters. Together with common motions and ages we confirm that NGC 5617 and Trumpler 22 are a primordial binary cluster pair in the Milky Way. [ABSTRACT FROM AUTHOR]

We present the results of a spectroscopic survey of red giants in the globular cluster Terzan 8 with the aim of studying its kinematics. We derived accurate radial velocities for 82 stars located in the innermost 7 arcmin from the cluster centre identifying 48 bona fide cluster members. The kinematics of the cluster have been compared with a set of dynamical models accounting for the effect of mass segregation and a variable fraction of binaries. The derived velocity dispersion appears to be larger than that predicted for mass-segregated stellar systems without binaries, indicating that either the cluster is dynamically young or it contains a large fraction of binaries (>30 per cent). We detected seven stars with a radial velocity compatible with the cluster systemic velocity but with chemical patterns which stray from those of both the cluster and the Galactic field. These stars are likely members of the Sagittarius stream surrounding this stellar system. [ABSTRACT FROM PUBLISHER]

TP53, one of the most important oncosuppressors, is frequently mutated in cancer. Several p53 mutant proteins escape proteolytic degradation and are highly expressed in an aberrant conformation often acquiring pro-oncogenic activities that promote tumor progression and resistance to therapy. Therefore, it has been vastly proposed that reactivation of wild-type (wt) function(s) from mutant p53 (mutp53) may have therapeutic significance. We have previously reported that Zn(II) restores a folded conformation from mutp53 misfolding, rescuing wild-type (wt) p53/DNA-binding and transcription activities. However, whether Zn(II) affects mutp53 stability has never been investigated. Here we show that a novel Zn(II) compound induced mutp53 (R175H) protein degradation through autophagy, the proteolytic machinery specifically devoted to clearing misfolded proteins. Accordingly, pharmacological or genetic inhibition of autophagy prevented Zn(II)-mediated mutp53H175 degradation as well as the ability of the Zn(II) compound to restore wtp53 DNA-binding and transcription activity from this mutant. By contrast, inhibition of the proteasome failed to do so, suggesting that autophagy is the main route for p53H175 degradation. Mechanistically, Zn(II) restored the wtp53 ability to induce the expression of the p53 target gene DRAM (damage-regulated autophagy modulator), a key regulator of autophagy, leading to autophagic induction. Accordingly, inhibition of wtp53 transactivation by pifithrin-α (PFT- α) impaired both autophagy and mutp53H175 degradation induced by curcumin-based zinc compound (Zn(II)-curc). Viewed together, our results uncover a novel mechanism employed by Zn(II)-curc to reactivate mutp53H175, which involves, at least in part, induction of mutp53 degradation via wtp53-mediated autophagy. [ABSTRACT FROM AUTHOR]

Stock 2 is a little-studied open cluster that shows an extended main-sequence turnoff (eMSTO). In order to investigate this phenomenon and characterise the cluster itself, we performed high-resolution spectroscopy in the framework of the Stellar Population Astrophysics project. We employed the High Accuracy Radial velocity Planet Searcher in the Northern hemisphere spectrograph at the Telescopio Nazionale Galileo (TNG). We completed our observations with additional spectra taken with the Catania Astrophysical Observatory Spectropolarimeter. We observed 46 stars (dwarfs and giants). They represent by far the largest sample collected for this cluster to date. We provide the stellar parameters, the extinction, and the radial and projected rotational velocities for most of the stars. Chemical abundances for 21 species with atomic numbers up to 56 have also been derived. We note a differential reddening in the cluster field with an average value of 0.27 mag. This appears the main cause for the observed eMSTO because it cannot be explained as the result of different rotational velocities, as found in other clusters. We estimate an age for Stock 2 of 450 ± 150 Ma, which corresponds to a MSTO stellar mass of ≈2.8 M⊙. The cluster mean radial velocity is about 8.0 km s−1. We find a solar-like metallicity for the cluster, [Fe/H] = −0.07 ± 0.06, compatible with its galactocentric distance. The chemical abundances of main-sequence stars and giants are compatible within the errors. The exceptions are barium and strontium, which are clearly overabundant in giants, and cobalt, which is only marginally overabundant. Finally, the chemical composition of Stock 2 is fully compatible with the composition observed in other open clusters of the Galactic thin-disc population. [ABSTRACT FROM AUTHOR]

We provide the largest and most homogeneous sample of α-element (Mg, Ca, Ti) and iron abundances for field RR Lyrae (RRLs; 162 variables) by using high-resolution spectra. The current measurements were complemented with similar abundances available in the literature for 46 field RRLs brought to our metallicity scale. We ended up with a sample of old (t ≥ 10 Gyr), low-mass stellar tracers (208 RRLs: 169 fundamental, 38 first overtone, and 1 mixed mode) covering 3 dex in iron abundance (−3.00 ≤ [Fe/H] ≤ 0.24). We found that field RRLs are ∼0.3 dex more α poor than typical halo tracers in the metal-rich regime ([Fe/H] ≥ −1.2), while in the metal-poor regime ([Fe/H] ≤ −2.2) they seem to be on average ∼0.1 dex more α enhanced. This is the first time that the depletion in α elements for solar iron abundances is detected on the basis of a large, homogeneous, and coeval sample of old stellar tracers. Interestingly, we also detected a close similarity in the [α/Fe] trend between α-poor, metal-rich RRLs and red giants (RGs) in the Sagittarius dwarf galaxy as well as between α-enhanced, metal-poor RRLs and RGs in ultrafaint dwarf galaxies. These results are supported by similar elemental abundances for 46 field horizontal branch stars. These stars share with RRLs the same evolutionary phase and the same progenitors. This evidence further supports the key role that old stellar tracers play in constraining the early chemical enrichment of the halo and, in particular, in investigating the impact that dwarf galaxies have had in the mass assembly of the Galaxy. [ABSTRACT FROM AUTHOR]

Open clusters are unique tracers of the history of our own Galaxy's disc. According to our membership analysis based on Gaia astrometry, out of the 226 potential clusters falling in the footprint of the GALactic Archaeology with HERMES (GALAH) survey or the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey, we find that 205 have secure members that were observed by at least one of the surveys. Furthermore, members of 134 clusters have high-quality spectroscopic data that we use to determine their chemical composition. We leverage this information to study the chemical distribution throughout the Galactic disc of 21 elements, from C to Eu. The radial metallicity gradient obtained from our analysis is −0.076 ± 0.009 dex kpc−1, which is in agreement with previous works based on smaller samples. Furthermore, the gradient in the [Fe/H]–guiding radius (r guid) plane is −0.073 ± 0.008 dex kpc−1. We show consistently that open clusters trace the distribution of chemical elements throughout the Galactic disc differently than field stars. In particular, at the given radius, open clusters show an age–metallicity relation that has less scatter than field stars. As such scatter is often interpreted as an effect of radial migration, we suggest that these differences are due to the physical selection effect imposed by our Galaxy: clusters that would have migrated significantly also had higher chances to get destroyed. Finally, our results reveal trends in the [X/Fe]– r guid–age space, which are important to understand production rates of different elements as a function of space and time. [ABSTRACT FROM AUTHOR]

Recent observations of resolved cold debris discs at tens of au have revealed that gaps could be a common feature in these Kuiper-belt analogues. Such gaps could be evidence for the presence of planets within the gaps or closer in near the edges of the disc. We present SPHERE observations of HD 92945 and HD 107146, two systems with detected gaps. We constrained the mass of possible companions responsible for the gap to 1–2  M Jup for planets located inside the gap and to less than 5  M Jup for separations down to 20 au from the host star. These limits allow us to exclude some of the possible configurations of the planetary systems proposed to explain the shape of the discs around these two stars. In order to put tighter limits on the mass at very short separations from the star, where direct-imaging data are less effective, we also combined our data with astrometric measurements from Hipparcos and Gaia and radial-velocity measurements. We were able to limit the separation and the mass of the companion potentially responsible for the proper-motion anomaly of HD 107146 to values of 2–7 au and 2–5  M Jup, respectively. [ABSTRACT FROM AUTHOR]

We performed the largest and most homogeneous spectroscopic survey of field RR Lyraes (RRLs). We secured ≈6300 high-resolution (HR, R ∼ 35,000) spectra for 143 RRLs (111 fundamental, RRab; 32 first-overtone, RRc). The atmospheric parameters were estimated by using the traditional approach and the iron abundances were measured by using an LTE line analysis. The resulting iron distribution shows a well-defined metal-rich tail approaching solar iron abundance. This suggests that field RRLs experienced a complex chemical enrichment in the early halo formation. We used these data to develop a new calibration of the ΔS method. This diagnostic, based on the equivalent widths of Ca ii K and three Balmer (Hδ,γ,β) lines, traces the metallicity of RRLs. For the first time, the new empirical calibration: (i) includes spectra collected over the entire pulsation cycle; (ii) includes RRc variables; (iii) relies on spectroscopic calibrators covering more than three dex in iron abundance; and (iv) provides independent calibrations based on one/two/three Balmer lines. The new calibrations were applied to a data set of both SEGUE-SDSS and degraded HR spectra totalling 6451 low-resolution (R ∼ 2000) spectra for 5001 RRLs (3439 RRab, 1562 RRc). This resulted in an iron distribution with a median η = −1.55 ± 0.01 and σ = 0.51 dex, in good agreement with literature values. We also found that RRc are 0.10 dex more metal-poor than RRab variables, and have a distribution with a smoother metal-poor tail. This finding supports theoretical prescriptions suggesting a steady decrease in the RRc number when moving from metal-poor to metal-rich stellar environments. [ABSTRACT FROM AUTHOR]

Context. Open clusters are excellent tracers of the chemical evolution of the Galactic disc. The spatial distribution of their elemental abundances, through the analysis of high-quality and high-resolution spectra, provides insight into the chemical evolution and mechanisms of element nucleosynthesis in regions characterised by different conditions (e.g. star formation efficiency and metallicity). Aims. In the framework of the Stellar Population Astrophysics (SPA) project, we present new observations and spectral analysis of four sparsely studied open clusters located in the solar neighbourhood, namely Collinder 350, Gulliver 51, NGC 7044, and Ruprecht 171. Methods. We exploit the HARPS-N spectrograph at the TNG telescope to acquire high-resolution optical spectra for 15 member stars of four clusters. We derive stellar parameters (Teff, log g, [Fe/H] and ξ) using both the equivalent width (EW) analysis and the spectral fitting technique. We compute elemental abundances for light, α-, iron-peak, and n-capture elements using the EW measurement approach. We investigate the origin of the correlation between metallicity and stellar parameters derived with the EW method for the coolest stars of the sample (Teff <  4300 K). The correlation is likely due to the challenging continuum setting and to a general inaccuracy of model atmospheres used to reproduce the conditions of very cool giant stars. Results. We locate the properties of our clusters in the radial distributions of metallicity and abundance ratios, comparing our results with clusters from the Gaia-ESO and APOGEE surveys. We present the [X/Fe]−[Fe/H] and [X/Fe]−RGC trends for elements in common between the two surveys. Finally, we derive the C and Li abundances as a function of the evolutionary phase and compare them with theoretical models. Conclusions. The SPA survey, with its high-resolution spectra, allows us to fully characterise the chemistry of nearby clusters. With a single set of spectra, we provide chemical abundances for a variety of chemical elements, which are comparable to those obtained in two of the largest surveys combined. The metallicities and abundance ratios of our clusters fit very well in the radial distributions defined by the recent literature, reinforcing the importance of star clusters to outline the spatial distribution of abundances in our Galaxy. Moreover, the abundances of C and Li, modified by stellar evolution during the giant phase, agree with evolutionary prescriptions (rotation-induced mixing) for their masses and metallicities. [ABSTRACT FROM AUTHOR]

Context. Detecting and characterising exoworlds around very young stars (age ≤10 Myr) are key aspects of exoplanet demographic studies, especially for understanding the mechanisms and timescales of planet formation and migration. Any reliable theory for such physical phenomena requires a robust observational database to be tested. However, detection using the radial velocity method alone can be very challenging because the amplitude of the signals caused by the magnetic activity of such stars can be orders of magnitude larger than those induced even by massive planets. Aims. We observed the very young (~2 Myr) and very active star V830 Tau with the HARPS-N spectrograph between October 2017 and March 2020 to independently confirm and characterise the previously reported hot Jupiter V830 Tau b (Kb = 68 ± 11 m s−1; mb sin ib = 0.57 ± 0.10 MJup; Pb = 4.927 ± 0.008 d). Methods. Because of the observed ~1 km s−1 radial velocity scatter that can clearly be attributed to the magnetic activity of V830 Tau, we analysed radial velocities extracted with different pipelines and modelled them using several state-of-the-art tools. We devised injection-recovery simulations to support our results and characterise our detection limits. The analysis of the radial velocities was aided by a characterisation of the stellar activity using simultaneous photometric and spectroscopic diagnostics. Results. Despite the high quality of our HARPS-N data and the diversity of tests we performed, we were unable to detect the planet V830 Tau b in our data and cannot confirm its existence. Our simulations show that a statistically significant detection of the claimed planetary Doppler signal is very challenging. Conclusions. It is important to continue Doppler searches for planets around young stars, but utmost care must be taken in the attempt to overcome the technical difficulties to be faced in order to achieve their detection and characterisation. This point must be kept in mind when assessing their occurrence rate, formation mechanisms, and migration pathways, especially without evidence of their existence from photometric transits. [ABSTRACT FROM AUTHOR]

We present the discovery of a white dwarf companion at ∼3.6 arcsec from GJ 3346, a nearby (π ∼ 42 mas) K star observed with SPHERE@VLT as part of an open time survey for faint companions to objects with significant proper motion discrepancies (Δμ) between Gaia DR1 and Tycho-2. Syrius-like systems like GJ 3346 AB, which include a main-sequence star and a white dwarf, can be difficult to detect because of the intrinsic faintness of the latter. They have, however, been found to be common contaminants for direct imaging (DI) searches. White dwarfs have in fact similar brightness to substellar companions in the infrared, while being much brighter in the visible bands like those used by Gaia. Combining our observations with Gaia DR2 and with several additional archival data sets, we were able to fully constrain the physical properties of GJ 3346 B, such as its effective temperature (11 × 103 ± 500 K) as well as the cooling age of the system (648 ± 58 Myr). This allowed us to better understand the system history and to partially explain the discrepancies previously noted in the age indicators for this object. Although further investigation is still needed, it seems that GJ 3346, which was previously classified as young, is in fact most likely to be older than 4 Gyr. Finally, given that the mass (0.58 ± 0.01 M⊙) and separation (85 au) of GJ 3346 B are compatible with the observed Δμ, this discovery represents a further confirmation of the potential of this kind of dynamical signatures as selection methods for DI surveys targeting faint, substellar companions. [ABSTRACT FROM AUTHOR]

Substellar companions at wide separation around stars hosting planets or brown dwarfs (BDs) yet close enough for their formation in the circumstellar disc are of special interest. In this Letter we report the discovery of a wide (projected separation ~1600:0, or 2400AU, and position angle 114.61°) companion of the GQLup A-B system, most likely gravitationally bound to it. A VLT/Xshooter spectrum shows that this star, 2MASS J15491331-3539118, is a bonafide low-mass (~0.15 M⊙) young stellar object (YSO) with stellar and accretion/ejection properties typical of Lupus YSOs of similar mass, and with kinematics consistent with that of the GQLup A-B system. A possible scenario for the formation of the triple system is that GQLupA and 2MASS J15491331-3539118 formed by fragmentation of a turbulent core in the Lup I filament, while GQLup B, the BD companion of GQLupA at 000:7, formed in situ by the fragmentation of the circumprimary disc. The recent discoveries that stars form along cloud filaments would favour the scenario of turbulent fragmentation for the formation of GQLupA and 2MASS J15491331-3539118. [ABSTRACT FROM AUTHOR]

Context. The study of high-contrast imaged brown dwarfs and exoplanets depends strongly on evolutionary models. To estimate the mass of a directly imaged substellar object, its extracted photometry or spectrum is used and adjusted with model spectra together with the estimated age of the system. These models still need to be properly tested and constrained. HD 4747B is a brown dwarf close to the H burning mass limit, orbiting a nearby (d = 19.25 ± 0.58 pc), solar-type star (G9V); it has been observed with the radial velocity method for over almost two decades. Its companion was also recently detected by direct imaging, allowing a complete study of this particular object. Aims. We aim to fully characterize HD 4747B by combining a well-constrained dynamical mass and a study of its observed spectral features in order to test evolutionary models for substellar objects and to characterize its atmosphere. Methods. We combined the radial velocity measurements of High Resolution Echelle Spectrometer (HIRES) and CORALIE taken over two decades and high-contrast imaging of several epochs from NACO, NIRC2, and SPHERE to obtain a dynamical mass. From the SPHERE data we obtained a low-resolution spectrum of the companion from Y to H band, and two narrow band-width photometric measurements in the K band. A study of the primary star also allowed us to constrain the age of the system and its distance. Results. Thanks to the new SPHERE epoch and NACO archival data combined with previous imaging data and high-precision radial velocity measurements, we were able to derive a well-constrained orbit. The high eccentricity (e = 0.7362 ± 0.0025) of HD 4747B is confirmed, and the inclination and the semi-major axis are derived (i = 47.3 ± 1.6°, a = 10.01 ± 0.21 au). We derive a dynamical mass of mB = 70.0 ± 1.6 MJup, which is higher than a previous study but in better agreement with the models. By comparing the object with known brown dwarfs spectra, we derive a spectral type of L9 and an effective temperature of 1350 ± 50 K. With a retrieval analysis we constrain the oxygen and carbon abundances and compare them with the values from the HR 8799 planets. [ABSTRACT FROM AUTHOR]

HD 163296 is a Herbig Ae/Be star known to host a protoplanetary disc with a ringed structure. To explain the disc features, previous works proposed the presence of planets embedded into the disc. We have observed HD 163296 with the near-infrared (NIR) branch of SPHERE composed by IRDIS (InfraRed Dual-band Imager and Spectrograph) and IFS (integral field spectrograph) with the aim to put tight constraints on the presence of substellar companions around this star. Despite the low rotation of the field of view during our observation we were able to put upper mass limits of few MJup around this object. These limits do not allow to give any definitive conclusion about the planets proposed through the disc characteristics. On the other hand, our results seem to exclude the presence of the only candidate proposed until now using direct imaging in the NIR even if some caution has to be taken considered the different wavelength bands of the two observations. [ABSTRACT FROM AUTHOR]

Aims. R Coronae Australis (R CrA) is the brightest star of the Coronet nebula of the Corona Australis (CrA) star forming region. This star is very red in color, probably due to dust absorption, and is strongly variable. High-contrast instruments allow for an unprecedented direct exploration of the immediate circumstellar environment of this star. Methods. We observed R CrA with the near-infrared (NIR) channels (IFS and IRDIS) of SPHERE at the Very Large Telescope (VLT). In this paper, we used four different epochs, three of which are from open time observations while one is from SPHERE guaranteed time. The data were reduced using the data reduction and handling pipeline and the SPHERE Data Center. We implemented custom IDL routines on the reduced data with the aim to subtract the speckle halo. We have also obtained pupil-tracking H-band (1.45−1.85 μm) observations with the VLT/SINFONI NIR medium-resolution (R ∼ 3000) spectrograph. Results. A companion was found at a separation of 0.156″ from the star in the first epoch and increasing to 0.184″ in the final epoch. Furthermore, several extended structures were found around the star, the most noteworthy of which is a very bright jet-like structure northeast from the star. The astrometric measurements of the companion in the four epochs confirm that it is gravitationally bound to the star. The SPHERE photometry and SINFONI spectrum, once corrected for extinction, point toward a spectral type object that is early M with a mass between 0.3 and 0.55 M⊙. The astrometric analyis provides constraints on the orbit paramenters: e ∼ 0.4, semimajor axis at 27–28 au, inclination of ∼70°, and a period larger than 30 yr. We were also able to put constraints of few MJup on the mass of possible other companions down to separations of few tens of au. [ABSTRACT FROM AUTHOR]

The overlap between the spectroscopic Galactic Archaeology with HERMES (GALAH) survey and Gaia provides a high-dimensional chemodynamical space of unprecedented size. We present a first analysis of a subset of this overlap, of 7066 dwarf, turn-off, and sub-giant stars. These stars have spectra from the GALAH survey and high parallax precision from the Gaia DR1 Tycho-Gaia Astrometric Solution. We investigate correlations between chemical compositions, ages, and kinematics for this sample. Stellar parameters and elemental abundances are derived from the GALAH spectra with the spectral synthesis code SPECTROSCOPY MADE EASY. We determine kinematics and dynamics, including action angles, from the Gaia astrometry and GALAH radial velocities. Stellar masses and ages are determined with Bayesian isochrone matching, using our derived stellar parameters and absolute magnitudes. We report measurements of Li, C, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, as well as Ba and we note that we have employed non-LTE calculations for Li, O, Al, and Fe. We show that the use of astrometric and photometric data improves the accuracy of the derived spectroscopic parameters, especially log g. Focusing our investigation on the correlations between stellar age, iron abundance [Fe/H], and mean alpha-enhancement [α/Fe] of the magnitude-selected sample, we recover the result that stars of the high-α sequence are typically older than stars in the low-α sequence, the latter spanning iron abundances of −0.7 <  [Fe/H] <  +0.5. While these two sequences become indistinguishable in [α/Fe] vs. [Fe/H] at the metal-rich regime, we find that age can be used to separate stars from the extended high-α and the low-α sequence even in this regime. When dissecting the sample by stellar age, we find that the old stars (>8 Gyr) have lower angular momenta Lz than the Sun, which implies that they are on eccentric orbits and originate from the inner disc. Contrary to some previous smaller scale studies we find a continuous evolution in the high-α-sequence up to super-solar [Fe/H] rather than a gap, which has been interpreted as a separate "high-α metal-rich" population. Stars in our sample that are younger than 10 Gyr, are mainly found on the low α-sequence and show a gradient in Lz from low [Fe/H] (Lz >  Lz, ⊙) towards higher [Fe/H] (Lz <  Lz, ⊙), which implies that the stars at the ends of this sequence are likely not originating from the close solar vicinity. [ABSTRACT FROM AUTHOR]

Context. Young planets are expected to cause cavities, spirals, and kinematic perturbations in protostellar disks that may be used to infer their presence. However, a clear detection of still-forming planets embedded within gas-rich disks is still rare. Aims. HD 169142 is a very young Herbig Ae-Be star surrounded by a pre-transitional disk, composed of at least three rings. While claims of sub-stellar objects around this star have been made previously, follow-up studies remain inconclusive. The complex structure of this disk is not yet well understood. Methods. We used the high contrast imager SPHERE at ESO Very large Telescope to obtain a sequence of high-resolution, high-contrast images of the immediate surroundings of this star over about three years in the wavelength range 0.95–2.25 μm. This enables a photometric and astrometric analysis of the structures in the disk. Results. While we were unable to definitively confirm the previous claims of a massive sub-stellar object at 0.1–0.15 arcsec from the star, we found both spirals and blobs within the disk. The spiral pattern may be explained as due to the presence of a primary, a secondary, and a tertiary arm excited by a planet of a few Jupiter masses lying along the primary arm, likely in the cavities between the rings. The blobs orbit the star consistently with Keplerian motion, allowing a dynamical determination of the mass of the star. While most of these blobs are located within the rings, we found that one of them lies in the cavity between the rings, along the primary arm of the spiral design. Conclusions. This blob might be due to a planet that might also be responsible for the spiral pattern observed within the rings and for the cavity between the two rings. The planet itself is not detected at short wavelengths, where we only see a dust cloud illuminated by stellar light, but the planetary photosphere might be responsible for the emission observed in the K1 and K2 bands. The mass ofthis putative planet may be constrained using photometric and dynamical arguments. While uncertainties are large, the mass should be between 1 and 4 Jupiter masses. The brightest blobs are found at the 1:2 resonance with this putative planet. [ABSTRACT FROM AUTHOR]

Aims. HD 142527 is one of the most frequently studied Herbig Ae/Be stars with a transitional disk that hosts a large cavity that is up to about 100 au in radius. For this reason, it has been included in the guaranteed time observation (GTO) SpHere INfrared survey for Exoplanets (SHINE) as part of the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) at the Very Large Telescope (VLT) in order to search for low-mass companions that might explain the presence of the gap. SHINE is a large survey within about 600 young nearby stars are observed with SPHERE with the aim to constrain the occurrence and orbital properties of the giant planet population at large (> 5 au) orbital separation around young stars. Methods. We used the IRDIFS observing mode of SPHERE (IRDIS short for infrared dual imaging and spectrograph plus IFS or integral field spectrograph) without any coronagraph in order to search for and characterize companions as close as 30 mas of the star. Furthermore, we present the first observations that ever used the sparse aperture mask (SAM) for SPHERE both in IRDIFS and IRDIFS_EXT modes. All the data were reduced using the dedicated SPHERE pipeline and dedicated algorithms that make use of the principal component analysis (PCA) and reference differential imaging (RDI) techniques. Results. We detect the accreting low–mass companion HD 142527B at a separation of 73 mas (11.4 au) from the star. No other companions with mass greater than 10 MJ are visible in the field of view of IFS (∼100 au centered on the star) or in the IRDIS field of view (∼400 au centered on the star). Measurements from IFS, SAM IFS, and IRDIS suggest an M6 spectral type for HD 142527B, with an uncertainty of one spectral subtype, compatible with an object of M = 0.11 ± 0.06 M⊙ and R = 0.15 ± 0.07 R⊙. The determination of the mass remains a challenge using contemporary evolutionary models, as they do not account for the energy input due to accretion from infalling material. We consider that the spectral type of the secondary may also be earlier than the type we derived from IFS spectra. From dynamical considerations, we further constrain the mass to 0.26+0.16−0.14 0. 26 − 0.14 + 0.16 $ 0.26^{+0.16}_{-0.14} $ M⊙, which is consistent with both our spectroscopic analysis and the values reported in the literature. Following previous methods, the lower and upper dynamical mass values correspond to a spectral type between M2.5 and M5.5 for the companion. By fitting the astrometric points, we find the following orbital parameters: a period of P = 35 − 137 yr; an inclination of i = 121 − 130°, a value of Ω = 124 − 135° for the longitude of node, and an 68% confidence interval of ∼18 − 57 au for the separation at periapsis. Eccentricity and time at periapsis passage exhibit two groups of values: ∼0.2–0.45 and ∼0.45–0.7 for e, and ∼2015–2020 and ∼2020–2022 for T0. While these orbital parameters might at first suggest that HD 142527B is not the companion responsible for the outer disk truncation, a previous hydrodynamical analysis of this system showed that they are compatible with a companion that is able to produce the large cavity and other observed features. [ABSTRACT FROM AUTHOR]

Several recent spectroscopic investigations have presented conflicting results on the existence of Na-rich asymptotic giant branch (AGB) stars in the Galactic globular cluster M 4 (NGC 6121). The studies disagree on whether or not Na-rich red giant branch (RGB) stars evolve to the AGB. For a sample of previously published HERMES/AAT AGB and RGB stellar spectra, we present a re-analysis of O, Na, and Fe abundances, and a new analysis of Mg and Al abundances; we also present CN band strengths for this sample, derived from low-resolution AAOmega spectra. Following a detailed literature comparison, we find that the AGB samples of all studies consistently show lower abundances of Na and Al, and are weaker in CN, than RGB stars in the cluster. This is similar to recent observations of AGB stars in NGC 6752 and M 62. In an attempt to explain this result, we present new theoretical stellar evolutionary models for M 4; however, these predict that all stars, including Na-rich RGB stars, evolve on to the AGB. We test the robustness of our abundance results using a variety of atmospheric models and spectroscopic methods; however, we do not find evidence that systematic modelling uncertainties can explain the apparent lack of Na-rich AGB stars in M 4. We conclude that an unexplained, but robust, discordance between observations and theory remains for the AGB stars in M 4. [ABSTRACT FROM AUTHOR]

Using data from the GALAH pilot survey, we determine properties of the Galactic thin and thick discs near the solar neighbourhood. The data cover a small range of Galactocentric radius (7.9 ≤ RGC ≤ 9.5 kpc), but extend up to 4 kpc in height from the Galactic plane, and several kpc in the direction of Galactic anti-rotation (at longitude 260° ≤ ℓ ≤ 280°). This allows us to reliably measure the vertical density and abundance profiles of the chemically and kinematically defined 'thick' and 'thin' discs of the Galaxy. The thin disc (low-α population) exhibits a steep negative vertical metallicity gradient, at d[M/H]/dz = -0.18 ± 0.01 dex kpc-1, which is broadly consistent with previous studies. In contrast, its vertical α-abundance profile is almost flat, with a gradient of d[α/M]/dz = 0.008 ± 0.002 dex kpc-1. The steep vertical metallicity gradient of the low-α population is in agreement with models where radial migration has a major role in the evolution of the thin disc. The thick disc (high-α population) has a weaker vertical metallicity gradient d[M/H]/dz = -0.058 ± 0.003 dex kpc-1. The α- abundance of the thick disc is nearly constant with height, d[α/M]/dz = 0.007 ± 0.002 dex kpc-1. The negative gradient in metallicity and the small gradient in [α/M] indicate that the high-α population experienced a settling phase, but also formed prior to the onset of major Type Ia supernova enrichment. We explore the implications of the distinct α-enrichments and narrow [α/M] range of the sub-populations in the context of thick disc formation. [ABSTRACT FROM AUTHOR]

Debris disks are usually detected through the infrared excess over the photospheric level of their host star. The most favorable stars for disk detection are those with spectral types between A and K, while the statistics for debris disks detected around low-mass M-type stars is very low, either because they are rare or because they are more difficult to detect. Terrestrial planets, on the other hand, may be common around M-type stars. Here, we report on the discovery of an extended (likely) debris disk around the M-dwarf GSC 07396-00759. The star is a wide companion of the close accreting binary V4046 Sgr. The system probably is a member of the β Pictoris Moving Group. We resolve the disk in scattered light, exploiting high-contrast, high-resolution imagery with the two nearinfrared subsystems of the VLT/SPHERE instrument, operating in the YJ bands and the H2H3 doublet. The disk is clearly detected up to 1.5'' (~110 au) from the star and appears as a ring, with an inclination i ~ 83°, and a peak density position at ~70 au. The spatial extension of the disk suggests that the dust dynamics is affected by a strong stellar wind, showing similarities with the AU Mic system that has also been resolved with SPHERE. The images show faint asymmetric structures at the widest separation in the northwest side. We also set an upper limit for the presence of giant planets to 2 MJ . Finally, we note that the 2 resolved disks around M-type stars of 30 such stars observed with SPHERE are viewed close to edge-on, suggesting that a significant population of debris disks around M dwarfs could remain undetected because of an unfavorable orientation. [ABSTRACT FROM AUTHOR]

It has been well established that Galactic Globular clusters (GCs) harbour more than one stellar population, distinguishable by the anticorrelations of light-element abundances (C-N, Na-O, and Mg-Al). These studies have been extended recently to the asymptotic giant branch (AGB). Here, we investigate the AGB of NGC6397 for the first time. We have performed an abundance analysis of high-resolution spectra of 47 red giant branch (RGB) and eight AGB stars, deriving Fe, Na, O, Mg, and Al abundances. We find that NGC6397 shows no evidence of a deficit in Na-rich AGB stars, as reported for some other GCs - the subpopulation ratios of the AGB and RGB in NGC6397 are identical, within uncertainties. This agrees with expectations from stellar theory. This GC acts as a control for our earlier work on the AGB of M4 (with contrasting results), since the same tools and methods were used. [ABSTRACT FROM AUTHOR]

As part of our on-going project on the homogeneous chemical characterisation of multiple stellar populations in globular clusters (GCs), we studied NGC 5634, associated to the Sagittarius dwarf spheroidal galaxy, using high-resolution spectroscopy of red giant stars collected with VLT/FLAMES. We present here the radial velocity distribution of the 45 observed stars, 43 of which are cluster members, the detailed chemical abundance of 22 species for the seven stars observed with UVES-FLAMES, and the abundance of six elements for stars observed with GIRAFFE. On our homogeneous UVES metallicity scale, we derived a low-metallicity [Fe/H] =-1.867 ± 0.019 ± 0.065 dex (±statistical ±systematic error) with s = 0.050 dex (7 stars). We found the normal anticorrelations between light elements (Na and O, Mg and Al), a signature of multiple populations typical of massive and old GCs. We confirm the associations of NGC 5634 to the Sgr dSph, from which the cluster was lost a few Gyr ago, on the basis of its velocity and position, and the abundance ratios of α and neutron capture elements. [ABSTRACT FROM AUTHOR]