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Ítem The Gaia -ESO Survey: Empirical determination of the precision of stellar radial velocities and projected rotation velocities(EDP Sciences, 2015-08) Jackson, R.J.; Jeffries, R.D.; Lewis, J.; Koposov, S.E.; Sacco, G.G.; Randich, S.; Asplund, M.; Binney, J.; Bonifacio, P.; Drew, J.E.; Feltzing, S.; Ferguson, A.M.N.; Micela, G.; Neguerela, I.; Prusti, T.; Rix, H.-W.; Vallenari, A.; Alfaro, E.J.; Allende Prieto, C.; Babusiaux, C.; Bensby, T.; Blomme, R.; Bragaglia, A.; Flaccomio, E.; Francois, P.; Hambly, N.; Irwin, M.; Korn, A.J.; Lanzafame, A.C.; Pancino, E.; Recio-Blanco, A.; Smiljanic, R.; Van Eck, S.; Walton, N.; Bayo, A.; Bergemann, M.; Carraro, G.; Costado, M.T.; Damiani, Edvardsson B.; Franciosini, E.; Frasca, A.; Heiter, U.; Hill, V.; Hourihane, A.; Jofré, P.; Lardo, C.; De Laverny, P.; Lind, K.; Magrini, L.; Marconi, G.; Martayan, C.; Masseron, T.; Monaco, L.; Prisinzano, L.; Sbordone, L.; Sousa, S.G.; Worley, C.C.; Zaggia, S.Context. The Gaia-ESO Survey (GES) is a large public spectroscopic survey at the European Southern Observatory Very Large Telescope. Aims. A key aim is to provide precise radial velocities (RVs) and projected equatorial velocities (v sin i) for representative samples of Galactic stars, which will complement information obtained by the Gaia astrometry satellite. Methods. We present an analysis to empirically quantify the size and distribution of uncertainties in RV and v sin i using spectra from repeated exposures of the same stars. Results. We show that the uncertainties vary as simple scaling functions of signal-to-noise ratio (S/N) and v sin i, that the uncertainties become larger with increasing photospheric temperature, but that the dependence on stellar gravity, metallicity and age is weak. The underlying uncertainty distributions have extended tails that are better represented by Student's t-distributions than by normal distributions. Conclusions. Parametrised results are provided, which enable estimates of the RV precision for almost all GES measurements, and estimates of the v sin i precision for stars in young clusters, as a function of S/N, v sin i and stellar temperature. The precision of individual high S/N GES RV measurements is 0.22-0.26 kms-1, dependent on instrumental configuration. © ESO, 2015.Ítem The Gaia -ESO Survey: Lithium measurements and new curves of growth(EDP Sciences, 2022-12-01) Franciosini, E.; Randich, S.; De Laverny, P.; Biazzo, K.; Feuillet, D.K.; Frasca, A.; Lind, K.; Prisinzano, L.; Tautvaišiene, G.; Lanzafame, A.C.; Smiljanic, R.; Gonneau, A.; Magrini, L.; Pancino, E.; Guiglion, G.; Sacco, G.G.; Sanna, N.; Gilmore, G.; Bonifacio, P.; Jeffries, R.D.; Micela, G.; Prusti, T.; Alfaro, E.J.; Bensby, T.; Bragaglia, A.; François, P.; Korn, A.J.; Van Eck, S.; Bayo, A.; Bergemann, M.; Carraro, G.; Heiter, U.; Hourihane, A.; Jofré, P.; Lewis, J.; Martayan, C.; Monaco, L.; Morbidelli, L.; Worley, C.C.; Zaggia, S.Context. The Gaia-ESO Survey (GES) is a large public spectroscopic survey that was carried out using the multi-object FLAMES spectrograph at the Very Large Telescope. The survey provides accurate radial velocities, stellar parameters, and elemental abundances for ~115 000 stars in all Milky Way components. Aims. In this paper, we describe the method adopted in the final data release to derive lithium equivalent widths (EWs) and abundances. Methods. Lithium EWs were measured using two different approaches for FGK and M-type stars, to account for the intrinsic differences in the spectra. For FGK stars, we fitted the lithium line using Gaussian components, while direct integration over a predefined interval was adopted for M-type stars. Care was taken to ensure continuity between the two regimes. Abundances were derived using a new set of homogeneous curves of growth that were derived specifically for GES, and which were measured on a synthetic spectral grid consistently with the way the EWs were measured. The derived abundances were validated by comparison with those measured by other analysis groups using different methods. Results. Lithium EWs were measured for ~40 000 stars, and abundances could be derived for ~38 000 of them. The vast majority of the measures (80%) have been obtained for stars in open cluster fields. The remaining objects are stars in globular clusters, or field stars in the Milky Way disc, bulge, and halo. Conclusions. The GES dataset of homogeneous lithium abundances described here will be valuable for our understanding of several processes, from stellar evolution and internal mixing in stars at different evolutionary stages to Galactic evolution. © 2022 EDP Sciences. All rights reserved.Ítem The Gaia -ESO Survey: Metallicity and kinematic trends in the Milky Way bulge(EDP Sciences, 2014-09) Rojas-Arriagada, A.; Recio-Blanco, A.; Hill, V.; De Laverny, P.; Schultheis, M.; Babusiaux, C.; Zoccali, M.; Minniti, D.; Gonzalez, O.A.; Feltzing, S.; Gilmore, G.; Randich, S.; Vallenari, A.; Alfaro, E.J.; Bensby, T.; Bragaglia, A.; Flaccomio, E.; Lanzafame, A.C.; Pancino, E.; Smiljanic, R.; Bergemann, M.; Costado, M.T.; Damiani, F.; Hourihane, A.; Jofré, P.; Lardo, C.; Magrini, L.; Maiorca, E.; Morbidelli, L.; Sbordone, L.; Worley, C.C.; Zaggia, S.; Wyse, R.Aims. Observational studies of the Milky Way bulge are providing increasing evidence of its complex chemo-dynamical patterns and morphology. Our intent is to use the iDR1 Gaia-ESO Survey (GES) data set to provide new constraints on the metallicity and kinematic trends of the Galactic bulge, exploring the viability of the currently proposed formation scenarios. Methods. We analyzed the stellar parameters and radial velocities of ∼1200 stars in five bulge fields wich are located in the region −10◦ < l < 7 ◦ and −10◦ < b < −4 ◦ . We use VISTA Variables in the Via Lactea (VVV) photometry to verify the internal consistency of the atmospheric parameters recommended by the consortium. As a by-product, we obtained reddening values using a semi-empirical Teff-color calibration. We constructed the metallicity distribution functions and combined them with photometric and radial velocity data to analyze the properties of the stellar populations in the observed fields. Results. From a Gaussian decomposition of the metallicity distribution functions, we unveil a clear bimodality in all fields, with the relative size of components depending of the specific position on the sky. In agreement with some previous studies, we find a mild gradient along the minor axis (−0.05 dex/deg between b = −6 ◦ and b = −10◦ ) that arises from the varying proportion of metal-rich and metal-poor components. The number of metal-rich stars fades in favor of the metal-poor stars with increasing b. The K-magnitude distribution of the metal-rich population splits into two peaks for two of the analyzed fields that intersects the near and far branches of the X-shaped bulge structure. In addition, two lateral fields at (l, b) = (7, −9) and (l, b) = (−10, −8) present contrasting characteristics. In the former, the metallicity distribution is dominated by metal-rich stars, while in the latter it presents a mix of a metal-poor population and and a metal-intermediate one, of nearly equal sizes. Finally, we find systematic differences in the velocity dispersion between the metal-rich and the metal-poor components of each field. Conclusions. The iDR1 bulge data show chemo-dynamical distributions that are consistent with varying proportions of stars belonging to (i) a metal-rich boxy/peanut X-shaped component, with bar-like kinematics; and (ii) a metal-poor more extended rotating structure with a higher velocity dispersion that dominates far from the Galactic plane. These first GES data already allow studying the detailed spatial dependence of the Galactic bulge populations, thanks to the analysis of individual fields with relatively high statistics.Ítem The Gaia -ESO Survey: Properties of newly discovered Li-rich giants(EDP Sciences, 2018-09) Smiljanic, R.; Franciosini, E.; Bragaglia, A.; Tautvaišiene, G.; Fu, X.; Pancino, E.; Adibekyan, V.; Sousa, S.G.; Randich, S.; Montalbán, J.; Pasquini, L.; Magrini, L.; Drazdauskas, A.; García, R.A.; Mathur, S.; Mosser, B.; Régulo, C.; De Assis Peralta, R.; Hekker, S.; Feuillet, D.; Valentini, M.; Morel, T.; Martell, S.; Gilmore, G.; Feltzing, S.; Vallenari, A.; Bensby, T.; Korn, A.J.; Lanzafame, A.C.; Recio-Blanco, A.; Bayo, A.; Carraro, G.; Costado, M.T.; Frasca, A.; Jofré, P.; Lardo, C.; De Laverny, P.; Lind, K.; Masseron, T.; Monaco, L.; Morbidelli, L.; Prisinzano, L.; Sbordone, L.; Zaggia, S.Aims. We report 20 new lithium-rich giants discovered within the Gaia-ESO Survey, including the first Li-rich giant with an evolutionary stage confirmed by CoRoT (Convection, Rotation and planetary Transits) data. We present a detailed overview of the properties of these 20 stars. Methods. Atmospheric parameters and abundances were derived in model atmosphere analyses using medium-resolution GIRAFFE or high-resolution UVES (Ultraviolet and Visual Echelle Spectrograph) spectra. These results are part of the fifth internal data release of the Gaia-ESO Survey. The Li abundances were corrected for non-local thermodynamical equilibrium effects. Other stellar properties were investigated for additional peculiarities (the core of strong lines for signs of magnetic activity, infrared magnitudes, rotational velocities, chemical abundances, and Galactic velocities). We used Gaia DR2 parallaxes to estimate distances and luminosities. Results. The giants have A(Li) > 2.2 dex. The majority of them (14 of 20 stars) are in the CoRoT fields. Four giants are located in the field of three open clusters, but are not members. Two giants were observed in fields towards the Galactic bulge, but likely lie in the inner disc. One of the bulge field giants is super Li-rich with A(Li) = 4.0 dex. Conclusions. We identified one giant with infrared excess at 22 μm. Two other giants, with large v sin i, might be Li-rich because of planet engulfment. Another giant is found to be barium enhanced and thus could have accreted material from a former asymptotic giant branch companion. Otherwise, in addition to the Li enrichment, the evolutionary stages are the only other connection between these new Li-rich giants. The CoRoT data confirm that one Li-rich giant is at the core-He burning stage. The other giants are concentrated in close proximity to the red giant branch luminosity bump, the core-He burning stages, or the early-asymptotic giant branch. This is very clear from the Gaia-based luminosities of the Li-rich giants. This is also seen when the CoRoT Li-rich giants are compared to a larger sample of 2252 giants observed in the CoRoT fields by the Gaia-ESO Survey, which are distributed throughout the red giant branch in the Teff-log g diagram. These observations show that the evolutionary stage is a major factor for the Li enrichment in giants. Other processes, such as planet accretion, contribute at a smaller scale. © ESO 2018.Ítem The Gaia -ESO survey: separating disk chemical substructures with cluster models∗: evidence of a separate evolution in the metal-poor thin disk(EDP Sciences, 2016-02) Rojas-Arriagada, A.; Recio-Blanco, A.; De Laverny, P.; Schultheis, M.; Guiglion, G.; Mikolaitis, S.; Kordopatis, G.; Hill, V.; Gilmore, G.; Randich, S.; Alfaro, E.J.; Bensby, T.; Koposov, S.E.; Costado, M.T.; Franciosini, E.; Hourihane, A.; Jofré, P.; Lardo, C.; Lewis, J.; Lind, K.; Magrini, L.; Monaco, L.; Morbidelli, L.; Sacco, G.G.; Worley, C.C.; Zaggia, S.; Chiappini, C.Context. Recent spectroscopic surveys have begun to explore the Galactic disk system on the basis of large data samples, with spatial distributions sampling regions well outside the solar neighborhood. In this way, they provide valuable information for testing spatial and temporal variations of disk structure kinematics and chemical evolution. Aims. The main purposes of this study are to demonstrate the usefulness of a rigorous mathematical approach to separate substructures of a stellar sample in the abundance-metallicity plane, and provide new evidence with which to characterize the nature of the metal poor end of the thin disk sequence. Methods. We used a Gaussian mixture model algorithm to separate in the [Mg/Fe] vs. [Fe/H] plane a clean disk star subsample (essentially at RGC < 10 kpc) from the Gaia-ESO survey (GES) internal data release 2 (iDR2). We aim at decomposing it into data groups highlighting number density and/or slope variations in the abundance-metallicity plane. An independent sample of disk red clump stars from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) was used to cross-check the identified features. Results. We find that the sample is separated into five groups associated with major Galactic components; the metal-rich end of the halo, the thick disk, and three subgroups for the thin disk sequence. This is confirmed with the sample of red clump stars from APOGEE. The three thin disk groups served to explore this sequence in more detail. The two metal-intermediate and metal-rich groups of the thin disk decomposition ([Fe/H] > −0.25 dex) highlight a change in the slope at solar metallicity. This holds true at different radial regions of the Milky Way. The distribution of Galactocentric radial distances of the metal-poor part of the thin disk ([Fe/H] < −0.25 dex) is shifted to larger distances than those of the more metal-rich parts. Moreover, the metal-poor part of the thin disk presents indications of a scale height intermediate between those of the thick and the rest of the thin disk, and it displays higher azimuthal velocities than the latter. These stars might have formed and evolved in parallel and/or dissociated from the inside out formation taking place in the internal thin disk. Their enhancement levels might be due to their origin from gas pre-enriched by outflows from the thick disk or the inner halo. The smooth trends of their properties (their spatial distribution with respect to the plane, in particular) with [Fe/H] and [Mg/Fe] suggested by the data indicates a quiet dynamical evolution, with no relevant merger events.Ítem The Gaia -ESO Survey: Sodium and aluminium abundances in giants and dwarfs: Implications for stellar and Galactic chemical evolution(EDP Sciences, 2016-05) Smiljanic, R.; Romano, D.; Bragaglia, A.; Donati, P.; Magrini, L.; Friel, E.; Jacobson, H.; Randich, S.; Ventura, P.; Lind, K.; Bergemann, M.; Nordlander, T.; Morel, T.; Pancino, E.; Tautvaišiene, G.; Adibekyan, V.; Tosi, M.; Vallenari, A.; Gilmore, G.; Bensby, T.; François, P.; Koposov, S.; Lanzafame, A.C.; Recio-Blanco, A.; Bayo, A.; Carraro, G.; Casey, A.R.; Costado, M.T.; Franciosini, E.; Heiter, U.; Hill, V.; Hourihane, A.; Jofré, P.; Lardo, C.; De Laverny, P.; Lewis, J.; Monaco, L.; Morbidelli, L.; Sacco, G.G.; Sbordone, L.; Sousa, S.G.; Worley, C.C.; Zaggia, S.Context. Stellar evolution models predict that internal mixing should cause some sodium overabundance at the surface of red giants more massive than ∼1.5–2.0 M . The surface aluminium abundance should not be affected. Nevertheless, observational results disagree about the presence and/or the degree of Na and Al overabundances. In addition, Galactic chemical evolution models adopting different stellar yields lead to very different predictions for the behavior of [Na/Fe] and [Al/Fe] versus [Fe/H]. Overall, the observed trends of these abundances with metallicity are not well reproduced. Aims. We readdress both issues, using new Na and Al abundances determined within the Gaia-ESO Survey. Our aim is to obtain better observa tional constraints on the behavior of these elements using two samples: i) more than 600 dwarfs of the solar neighborhood and of open clusters and ii) low- and intermediate-mass clump giants in six open clusters. Methods. Abundances were determined using high-resolution UVES spectra. The individual Na abundances were corrected for nonlocal thermo dynamic equilibrium effects. For the Al abundances, the order of magnitude of the corrections was estimated for a few representative cases. For giants, the abundance trends with stellar mass are compared to stellar evolution models. For dwarfs, the abundance trends with metallicity and age are compared to detailed chemical evolution models. Results. Abundances of Na in stars with mass below ∼2.0 M , and of Al in stars below ∼3.0 M , seem to be unaffected by internal mixing processes. For more massive stars, the Na overabundance increases with stellar mass. This trend agrees well with predictions of stellar evolution ary models. For Al, our only cluster with giants more massive than 3.0 M , NGC 6705, is Al enriched. However, this might be related to the environment where the cluster was formed. Chemical evolution models that well fit the observed [Na/Fe] vs. [Fe/H] trend in solar neighborhood dwarfs cannot simultaneously explain the run of [Al/Fe] with [Fe/H], and vice versa. The comparison with stellar ages is hampered by severe uncertainties. Indeed, reliable age estimates are available for only a half of the stars of the sample. We conclude that Al is underproduced by the models, except for stellar ages younger than about 7 Gyr. In addition, some significant source of late Na production seems to be missing in the models. Either current Na and Al yields are affected by large uncertainties, and/or some important Galactic source(s) of these elements has as yet not been taken into account.Ítem The Gaia -ESO Survey: The origin and evolution of s -process elements(EDP Sciences, 2018-09) Magrini, L.; Spina, L.; Randich, S.; Friel, E.; Kordopatis, G.; Worley, C.; Pancino, E.; Bragaglia, A.; Donati, P.; Tautvaišienė, G.; Bagdonas, V.; Delgado-Mena, E.; Adibekyan, V.; Sousa, S.G.; Jiménez-Esteban, F.M.; Sanna, N.; Roccatagliata, V.; Bonito, R.; Sbordone, L.; Duffau, S.; Gilmore, G.; Feltzing, S.; Jeffries, R.D.; Vallenari, A.; Alfaro, E.J.; Bensby, T.; Francois, P.; Koposov, S.; Korn, A.J.; Recio-Blanco, A.; Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A.R.; Costado, M.T.; Damiani, F.; Franciosini, E.; Frasca, A.; Hourihane, A.; Jofré, P.; De Laverny, P.; Lewis, J.; Masseron, T.; Monaco, L.; Morbidelli, L.; Prisinzano, L.; Sacco, G.; Zaggia, S.Context. Several works have found an increase of the abundances of the s-process neutron-capture elements in the youngest Galactic stellar populations. These trends provide important constraints on stellar and Galactic evolution and they need to be confirmed with large and statistically significant samples of stars spanning wide age and distance intervals. Aims. We aim to trace the abundance patterns and the time evolution of five s-process elements - two belonging to the first peak, Y and Zr, and three belonging to the second peak, Ba, La, and Ce - using the Gaia-ESO IDR5 results for open clusters and disc stars. Methods. From the UVES spectra of cluster member stars, we determined the average composition of clusters with ages >0.1 Gyr. We derived statistical ages and distances of field stars, and we separated them into thin and thick disc populations. We studied the time-evolution and dependence on metallicity of abundance ratios using open clusters and field stars whose parameters and abundances were derived in a homogeneous way. Results. Using our large and homogeneous sample of open clusters, thin and thick disc stars, spanning an age range larger than 10 Gyr, we confirm an increase towards young ages of s-process abundances in the solar neighbourhood. These trends are well defined for open clusters and stars located nearby the solar position and they may be explained by a late enrichment due to significant contribution to the production of these elements from long-living low-mass stars. At the same time, we find a strong dependence of the s-process abundance ratios on the Galactocentric distance and on the metallicity of the clusters and field stars. Conclusions. Our results, derived from the largest and most homogeneous sample of s-process abundances in the literature, confirm the growth with decreasing stellar ages of the s-process abundances in both field and open cluster stars. At the same time, taking advantage of the abundances of open clusters located in a wide Galactocentric range, these results offer a new perspective on the dependence of the s-process evolution on the metallicity and star formation history, pointing to different behaviours at various Galactocentric distances. © 2018 ESO.Ítem The Gaia-ESO survey: A quiescent milky way with no significant dark/stellar accreted disc(Oxford University Press, 2015-07) Ruchti, G.R.; Read, J.I.; Feltzing, S.; Serenelli, A.M.; McMillan, P.; Lind, K.; Bensby, T.; Bergemann, M.; Asplund, M.; Vallenari, A.; Flaccomio, E.; Pancino, E.; Korn, A.J.; Recio-Blanco, A.; Bayo, A.; Carraro, G.; Costado, M.; Damiani, F.; Heiter, U.; Hourihane, A.; Jofré, P.; Kordopatis, G.; Lardo, C.; De Laverny, P.; Monaco, L.; Morbidelli, L.; Sbordone, L.; Worley, C.C.; Zaggia, S.According to our current cosmological model, galaxies like the Milky Way are expected to experience many mergers over their lifetimes. The most massive of the merging galaxies will be dragged towards the disc plane, depositing stars and dark matter into an accreted disc structure. In this work, we utilize the chemodynamical template developed in Ruchti et al. to hunt for accreted stars. We apply the template to a sample of 4675 stars in the third internal data release from the Gaia-ESO Spectroscopic Survey. We find a significant component of accreted halo stars, but find no evidence of an accreted disc component. This suggests that the Milky Way has had a rather quiescent merger history since its disc formed some 8-10 billion years ago and therefore possesses no significant dark matter disc. © 2015 The Authors.Ítem The Gaia-ESO Survey: Insights into the inner-disc evolution from open clusters(EDP Sciences, 2015-08) Magrini, L.; Randich, S.; Donati, P.; Bragaglia, A.; Adibekyan, V.; Romano, D.; Smiljanic, R.; Blanco-Cuaresma, S.; Tautvaišiene, G.; Friel, E.; Overbeek, J.; Jacobson, H.; Cantat-Gaudin, T.; Vallenari, A.; Sordo, R.; Pancino, E.; Geisler, D.; San Roman, I.; Villanova, S.; Casey, A.; Hourihane, A.; Worley, C.C.; Francois, P.; Gilmore, G.; Bensby, T.; Flaccomio, E.; Korn, A.J.; Recio-Blanco Carraro, G.; Costado, M.T.; Franciosini, E.; Heiter, U.; Jofré, P.; Lardo, C.; De Laverny, P.; Monaco, L.; Morbidelli, L.; Sacco, G.; Sousa, S.G.; Zaggia, S.Context. The inner disc, which links the thin disc with the bulge, has been somewhat neglected in the past because of the intrinsic difficulties in its study, among which crowding and high extinction. Open clusters located in the inner disc are among thebest tracers of its chemistry at different ages and distances. Aims. We analyse the chemical patterns of four open clusters located within 7 kpc of the Galactic centre and of field stars to infer the properties of the inner disc with the Gaia-ESO survey idr2/3 data release. Methods. We derive the parameters of the newly observed cluster, Berkeley 81, finding an age of about 1 Gyr and a Galactocentric distance of ∼5.4 kpc. We construct the chemical patterns of clusters and we compare them with those of field stars in the solar neighbourhood and in the inner-disc samples. Results. Comparing the three populations we observe that inner-disc clusters and field stars are both, on average, enhanced in [O/Fe], [Mg/Fe], and [Si/Fe]. Using the idr2/3 results of M67, we estimate the non-local thermodynamic equilibrium (NLTE) effect on the abundances of Mg and Si in giant stars. After empirically correcting for NLTE effects, we note that NGC 6705 and Be 81 still have a high [α/Fe]. Conclusions. The location of the four open clusters and of the field population reveals that the evolution of the metallicity [Fe/H] and of [α/Fe] can be explained within the framework of a simple chemical evolution model: both [Fe/H] and [α/Fe] of Trumpler 20 and of NGC 4815 are in agreement with expectations from a simple chemical evolution model. On the other hand, NGC 6705, and to a lesser degree Berkeley 81, have higher [α/Fe] than expected for their ages, location in the disc, and metallicity. These differences might originate from local enrichment processes as explained in the inhomogeneous evolution framework. © ESO 2015.