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Full list of authors: Duffau, S.; Caffau, E.; Sbordone, L.; Bonifacio, P.; Andrievsky, S.; Korotin, S.; Babusiaux, C.; Salvadori, S.; Monaco, L.; François, P.; Skúladóttir, Á.; Bragaglia, A.; Donati, P.; Spina, L.; Gallagher, A. J.; Ludwig, H. -G.; Christlieb, N.; Hansen, C. J.; Mott, A.; Steffen, M. Zaggia, S.; Blanco-Cuaresma, S.; Calura, F.; Friel, E.; Jiménez-Esteban, F. M.; Koch, A.; Magrini, L.; Pancino, E.; Tang, B.; Tautvaišienė, G.; Vallenari, A.; Hawkins, K.; Gilmore, G.; Randich, S.; Feltzing, S.; Bensby, T.; Flaccomio, E.; Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Franciosini, E.; Hourihane, A.; Jofré, P.; Lardo, C.; Lewis, J.; Morbidelli, L.; Sousa, S. G.; Worley, C. C., Context. Due to their volatile nature, when sulphur and zinc are observed in external galaxies, their determined abundances represent the gas-phase abundances in the interstellar medium. This implies that they can be used as tracers of the chemical enrichment of matter in the Universe at high redshift. Comparable observations in stars are more difficult and, until recently, plagued by small number statistics. Aims. We wish to exploit the Gaia-ESO Survey (GES) data to study the behaviour of sulphur and zinc abundances of a large number of Galactic stars, in a homogeneous way. Methods. By using the UVES spectra of the GES sample, we are able to assemble a sample of 1301 Galactic stars, including stars in open and globular clusters in which both sulphur and zinc were measured. Results. We confirm the results from the literature that sulphur behaves as an α-element. We find a large scatter in [Zn/Fe] ratios among giant stars around solar metallicity. The lower ratios are observed in giant stars at Galactocentric distances less than 7.5 kpc. No such effect is observed among dwarf stars, since they do not extend to that radius. Conclusions. Given the sample selection, giants and dwarfs are observed at different Galactic locations, and it is plausible, and compatible with simple calculations, that Zn-poor giants trace a younger population more polluted by SN Ia yields. It is necessary to extend observations in order to observe both giants and dwarfs at the same Galactic location. Further theoretical work on the evolution of zinc is also necessary. © 2017 ESO., This work was based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 188.B-3002. These data products have been processed by the Cambridge Astronomy Survey Unit (CASU) at the Institute of Astronomy, University of Cambridge, and by the FLAMES/UVES reduction team at INAF/Osservatorio Astrofisico di Arcetri. These data have been obtained from the Gaia-ESO Survey Data Archive, prepared and hosted by the Wide Field Astronomy Unit, Institute for Astronomy, University of Edinburgh, which is funded by the UK Science and Technology Facilities Council. This work was partly supported by the European Union FP7 programme through ERC grant number 320360 and by the Leverhulme Trust through grant RPG-2012-541. We acknowledge the support from INAF and Ministero dell' Istruzione, dell' Universita e della Ricerca (MIUR) in the form of the grant "Premiale VLT 2012 and PRIN-INAF 2014". The results presented here benefit from discussions held during the Gaia-ESO workshops and conferences supported by the ESF (European Science Foundation) through the GREAT Research Network Programme. Support for S. D. and L. Sbordone was provided by Chile's Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. The project was funded by FONDATION MERAC. S. S. is supported by the European Commission through a Marie Sklodowska-Curie Fellowship, project PRIMORDIAL, grant agreement: 700907. S.M.A. and S.A.K. acknowledge the SCOPES grant No. IZ73Z0-152485 for financial support. L.M. acknowledges support from "Proyecto interno" #803 of the Universidad Andres Bello. M.T.C. acknowledges the financial support from the Spanish Ministerio de Economia y Competitividad, through grant AYA2013-40611-P. T.B. and S.F. were funded by the project grant "The New Milky Way" from Knut and Alice Wallenberg Foundation. S.G.S. acknowledges the support by Fundacao para a Ciencia e Tecnologia (FCT) through national funds and a research grant (project ref. UID/FIS/04434/2013, and PTDC/FIS-AST/7073/2014). S.G.S. also acknowledges the support from FCT through Investigador FCT contract of reference IF/00028/2014 and POPH/FSE (EC) by FEDER funding through the program Programa Operacional de Factores de Competitividade - COMPETE. L. Spina acknowledges the support from FAPESP (2014/15706-9). R.S. acknowledges support the Polish Ministry of Science and Higher Education.

We characterize the selection function of RAVE using 2MASS as our underlying population, which we assume represents all stars which could have potentially been observed. We evaluate the completeness fraction as a function of position, magnitude, and color in two ways: first, on a field-by-field basis, and second, in equal-size areas on the sky. Then, we consider the effect of the RAVE stellar parameter pipeline on the final resulting catalogue, which in principle limits the parameter space over which our selection function is valid. Our final selection function is the product of the completeness fraction and the selection function of the pipeline. We then test if the application of the selection function introduces biases in the derived parameters. To do this, we compare a parent mock catalogue generated using Galaxia with a mock-RAVE catalogue where the selection function of RAVE has been applied. We conclude that for stars brighter than I = 12, between $4000 \rm K < T_{\rm eff} < 8000 \rm K$ and $0.5 < \rm{log}\,g < 5.0$, RAVE is kinematically and chemically unbiased with respect to expectations from Galaxia., 14 pages, 12 figures, accepted for publication in MNRAS

Context. The extensive stellar spectroscopic datasets that are available for studies in Galactic Archeaology thanks to, for example, the Gaia-ESO Survey, now benefit from having a significant number of targets that overlap with asteroseismology projects such as Kepler, K2, and CoRoT. Combining the measurements from spectroscopy and asteroseismology allows us to attain greater accuracy with regard to the stellar parameters needed to characterise the stellar populations of the Milky Way. Aims. The aim of this Gaia-ESO Survey special project is to produce a catalogue of self-consistent stellar parameters by combining measurements from high-resolution spectroscopy and precision asteroseismology. Methods. We carried out an iterative analysis of 90 K2@Gaia-ESO red giants. The spectroscopic values of Teff were used as input in the seismic analysis to obtain log g values. The seismic estimates of log g were then used to re-determine the spectroscopic values of Teff and [Fe/H]. Only one iteration was required to obtain parameters that are in good agreement for both methods and, thus, to obtain the final stellar parameters. A detailed analysis of outliers was carried out to ensure a robust determination of the parameters. The results were then combined with Gaia DR2 data to compare the seismic log g with a parallax-based log g and to investigate instances of variations in the velocity and possible binaries within the dataset. Results. This analysis produced a high-quality catalogue of stellar parameters for 90 red giant stars from K2@Gaia-ESO that were determined through iterations between spectroscopy and asteroseismology. We compared the seismic gravities with those based on Gaia parallaxes to find an offset which is similar to other studies that have used asteroseismology. Our catalogue also includes spectroscopic chemical abundances and radial velocities, as well as indicators for possible binary detections.

Full list of authors: Magrini, L.; Randich, S.; Kordopatis, G.; Prantzos, N.; Romano, D.; Chieffi, A.; Limongi, M.; François, P.; Pancino, E.; Friel, E.; Bragaglia, A.; Tautvaišienė, G.; Spina, L.; Overbeek, J.; Cantat-Gaudin, T.; Donati, P.; Vallenari, A.; Sordo, R.; Jiménez-Esteban, F. M.; Tang, B. Drazdauskas, A.; Sousa, S.; Duffau, S.; Jofré, P.; Gilmore, G.; Feltzing, S.; Alfaro, E.; Bensby, T.; Flaccomio, E.; Koposov, S.; Lanzafame, A.; Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Franciosini, E.; Hourihane, A.; Lardo, C.; Lewis, J.; Monaco, L.; Morbidelli, L.; Sacco, G.; Sbordone, L.; Worley, C. C.; Zaggia, S., Context. The spatial distribution of elemental abundances in the disc of our Galaxy gives insights both on its assembly process and subsequent evolution, and on the stellar nucleogenesis of the different elements. Gradients can be traced using several types of objects as, for instance, (young and old) stars, open clusters, HII regions, planetary nebulae. Aims. We aim to trace the radial distributions of abundances of elements produced through different nucleosynthetic channels - the α-elements O, Mg, Si, Ca and Ti, and the iron-peak elements Fe, Cr, Ni and Sc - by use of the Gaia-ESO IDR4 results for open clusters and young-field stars. Methods. From the UVES spectra of member stars, we have determined the average composition of clusters with ages > 0.1 Gyr. We derived statistical ages and distances of field stars. We traced the abundance gradients using the cluster and field populations and compared them with a chemo-dynamical Galactic evolutionary model. Results. The adopted chemo-dynamical model, with the new generation of metallicity-dependent stellar yields for massive stars, is able to reproduce the observed spatial distributions of abundance ratios, in particular the abundance ratios of [O/Fe] and [Mg/Fe] in the inner disc (5 kpc, The results presented here benefited from discussions in three Gaia-ESO workshops supported by the ESF (European Science Foundation) through the GREAT (Gaia Research for European Astronomy Training) Research Network Program (Science meetings 3855, 4127 and 4415). This work was partially supported by the Gaia Research for European Astronomy Training (GREAT-ITN) Marie Curie network, funded through the European Union Seventh Framework Programme [FP7/2007-2013] under grant agreement No. 264895. This work was partly supported through the European Research Council grant 320360: The Gaia-ESO Milky Way Survey. G.T. and A.D. acknowledge support by the Research Council of Lithuania (MIP-082/2015). This research has been partially supported by the National Institute for Astrophysics (INAF) through the grant PRIN-2014 ("Transient Universe, unveiling new types of stellar explosions with PESSTO"). F.J.E. acknowledges financial support from the Spacetec-CM project (S2013/ICE-2822). S.F. and T.B. are supported by the project grant "The New Milky Way" from the Knut and Alice Wallenberg Foundation. Support for S.D. was provided by the Chile's Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS.

Although many quasars and related objects are variable at both optical and radio frequencies, the relationship, if any, between these variations is unclear. In particular, only three objects, OJ287 (ref. 1), 0235 + 164 (ref. 2) and 0420 – 01 (ref. 3), have shown well correlated radio–optical variability. The first two are BL Lac objects and showed little or no time delay between the radio and optical variations. The last object is a quasar, and underwent a radio flare some 2 years after a significant optical outburst. Optical observations of another quasar, PKS1921 – 29, which may also show correlated radio and optical variability are reported here.

The distribution of enriched material in the stars and gas of our Galaxy contains information pertaining to the chemical evolution of the Milky Way from its formation epoch to the present, providing general constraints on theories of galaxy formation. Detailed studies of the metallicities of well-defined samples of long-lived G-dwarf stars in the solar neighbourhood have ruled out the ‘simple closed-box’ model of galactic chemical evolution—too few very metal-poor stars are observed1–3. The weakest assumption inherent in this model is that the galactic disk formed and evolved as a closed system. Allowing accretion of gas, either metal-enriched or primordial (the latter requiring a particular dependence of star formation on gas density), can yield an improved fit to the observations3. However, secondary infall from the galactic extreme spheroid provides only a slight alleviation of this ‘G-dwarf problem’4. Here we show that consideration of the chemical properties of the thick-disk population of the Galaxy5,6 results in a self-consistent model for galactic chemical evolution.

It has been widely accepted that large amounts of ‘missing’ mass must be present in spiral galaxies to explain both the small-scale and large-scale kinematic observations1. The small-scale data (velocity dispersions in the solar vicinity) refer to the volume within a few hundred parsecs of the Sun, and indicate that 25–50% of the gravitating mass has no detected luminous counterpart2–4. The large-scale data (velocity dispersions and rotation curves) show that this non-luminous component becomes increasingly important with increasing galactocentric distance, and is the dominant mass in the outer regions of galaxies, and in total. It is usually assumed that both the local and global missing mass are the same substance although no plausible candidate for this substance is known. The most widely assumed, and most conservative, candidate is a large population of very low-luminosity M dwarfs. These stars are attractive, both because they exist in large numbers, and because their mass (M) to light (L) ratios are similar to those needed to explain flat rotation curves (M/L ∼ 100–1,000). Finally, they are of very low intrinsic luminosity, and it is therefore observationally very difficult to determine their true space density from blue or visual surveys. We present here new observational results which show that low-luminosity M dwarfs are unlikely to provide the large-scale missing mass, and cannot provide the small-scale missing mass.

Observations of the Population II stars in external spiral galaxies show the domination of a metal-rich stars over metal-poor ones outward from the center for some distance, farther than which the metal-poor component dominates. This apparent contradiction between the properties of Population II in the Galaxy and in external spirals is resolved here by identifying the vast majority of spatially defined Population II stars in the solar neighborhood not with the metal-poor subdwarfs but with stars in the thick-disk component. Spatially defined Population II and metallicity-defined Population II are essentially distinct populations. Implications of this proposal for disk galaxy formation and evolution are discussed. It is shown how detailed information about the element ratios present in spheroid stars can place constraints on the timescale on which the metal-poor system formed and how homogeneous the protogalaxy could have been at this time. 109 references.

Stellar-occultation predictions are presented for Uranus and Neptune covering the period 1987-1990, based on automated scans of R and I plates taken with the UK Schmidt Telescope in Australia. These scans have revealed many late-type or highly reddened stars suitable for stellar-occultation observations at 2.2 microns that were missed in previous searches of yellow-sensitive astrographic plates (Mink and Klemola, 1985). Comparisons involving several hundred stars measured by Mink and Klemola (1985) indicate that the internal random errors in the stellar positions estimated here are less than about 0.2 arcsec, comparable to the precision reached using conventional astrographic methods. In addition, JHK photometry was obtained for many of the Neptune stars, which is used to establish an empirical (I-K) vs (R-I) calibration for the remaining occultation candidates, and thus provide estimates of their K magnitudes.