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27 results on '"Nordlander, T."'

3. The Gaia-ESO survey: Mapping the shape and evolution of the radial abundance gradients with open clusters

Author

Magrini, L., primary, Viscasillas Vázquez, C., additional, Spina, L., additional, Randich, S., additional, Romano, D., additional, Franciosini, E., additional, Recio-Blanco, A., additional, Nordlander, T., additional, D’Orazi, V., additional, Baratella, M., additional, Smiljanic, R., additional, Dantas, M. L. L., additional, Pasquini, L., additional, Spitoni, E., additional, Casali, G., additional, Van der Swaelmen, M., additional, Bensby, T., additional, Stonkute, E., additional, Feltzing, S., additional, Sacco, G. G., additional, Bragaglia, A., additional, Pancino, E., additional, Heiter, U., additional, Biazzo, K., additional, Gilmore, G., additional, Bergemann, M., additional, Tautvaišienė, G., additional, Worley, C., additional, Hourihane, A., additional, Gonneau, A., additional, and Morbidelli, L., additional

Published
2023
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8. The GALAH Survey: non-LTE departure coefficients for large spectroscopic surveys.

Author

Amarsi, A. M., Lind, K., Osorio, Y., Nordlander, T., Bergemann, M., Reggiani, H., Wang, E. X., Buder, S., Asplund, M., Barklem, P. S., Wehrhahn, A., Skúladóttir, Á., Kobayashi, C., Karakas, A. I., Gao, X. D., Bland-Hawthorn, J., De Silva, G. M., Kos, J., Lewis, G. F., and Martell, S. L.

Subjects
ALKALINE earth metals, LOCAL thermodynamic equilibrium, BIG data, STELLAR spectra, INELASTIC collisions, ATOMIC models, STELLAR atmospheres
Abstract

Massive sets of stellar spectroscopic observations are rapidly becoming available and these can be used to determine the chemical composition and evolution of the Galaxy with unprecedented precision. One of the major challenges in this endeavour involves constructing realistic models of stellar spectra with which to reliably determine stellar abundances. At present, large stellar surveys commonly use simplified models that assume that the stellar atmospheres are approximately in local thermodynamic equilibrium (LTE). To test and ultimately relax this assumption, we have performed non-LTE calculations for 13 different elements (H, Li, C, N, O, Na, Mg, Al, Si, K, Ca, Mn, and Ba), using recent model atoms that have physically-motivated descriptions for the inelastic collisions with neutral hydrogen, across a grid of 3756 1D MARCS model atmospheres that spans 3000 ≤ Teff∕K ≤ 8000, − 0.5 ≤log g∕cm s−2 ≤ 5.5, and − 5 ≤ [Fe/H] ≤ 1. We present the grids of departure coefficients that have been implemented into the GALAH DR3 analysis pipeline in order to complement the extant non-LTE grid for iron. We also present a detailed line-by-line re-analysis of 50 126 stars from GALAH DR3. We found that relaxing LTE can change the abundances by between − 0.7 dex and + 0.2 dex for different lines and stars. Taking departures from LTE into account can reduce the dispersion in the [A/Fe] versus [Fe/H] plane by up to 0.1 dex, and it can remove spurious differences between the dwarfs and giants by up to 0.2 dex. The resulting abundance slopes can thus be qualitatively different in non-LTE, possibly with important implications for the chemical evolution of our Galaxy. The grids of departure coefficients are publicly available and can be implemented into LTE pipelines to make the most of observational data sets from large spectroscopic surveys. [ABSTRACT FROM AUTHOR]

Published
2020
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14. A test field forGaia

Author

Frémat, Y., primary, Altmann, M., additional, Pancino, E., additional, Soubiran, C., additional, Jofré, P., additional, Damerdji, Y., additional, Heiter, U., additional, Royer, F., additional, Seabroke, G., additional, Sordo, R., additional, Blanco-Cuaresma, S., additional, Jasniewicz, G., additional, Martayan, C., additional, Thévenin, F., additional, Vallenari, A., additional, Blomme, R., additional, David, M., additional, Gosset, E., additional, Katz, D., additional, Viala, Y., additional, Boudreault, S., additional, Cantat-Gaudin, T., additional, Lobel, A., additional, Meisenheimer, K., additional, Nordlander, T., additional, Raskin, G., additional, Royer, P., additional, and Zorec, J., additional

Published
2016
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15. TheGaia-ESO Survey: Sodium and aluminium abundances in giants and dwarfs

Author

Smiljanic, R., primary, Romano, D., additional, Bragaglia, A., additional, Donati, P., additional, Magrini, L., additional, Friel, E., additional, Jacobson, H., additional, Randich, S., additional, Ventura, P., additional, Lind, K., additional, Bergemann, M., additional, Nordlander, T., additional, Morel, T., additional, Pancino, E., additional, Tautvaišien*error*ė, G., additional, Adibekyan, V., additional, Tosi, M., additional, Vallenari, A., additional, Gilmore, G., additional, Bensby, T., additional, François, P., additional, Koposov, S., additional, Lanzafame, A. C., additional, Recio-Blanco, A., additional, Bayo, A., additional, Carraro, G., additional, Casey, A. R., additional, Costado, M. T., additional, Franciosini, E., additional, Heiter, U., additional, Hill, V., additional, Hourihane, A., additional, Jofré, P., additional, Lardo, C., additional, de Laverny, P., additional, Lewis, J., additional, Monaco, L., additional, Morbidelli, L., additional, Sacco, G. G., additional, Sbordone, L., additional, Sousa, S. G., additional, Worley, C. C., additional, and Zaggia, S., additional

Published
2016
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16. GaiaFGK benchmark stars: abundances ofαand iron-peak elements

Author

Jofré, P., primary, Heiter, U., additional, Soubiran, C., additional, Blanco-Cuaresma, S., additional, Masseron, T., additional, Nordlander, T., additional, Chemin, L., additional, Worley, C. C., additional, Van Eck, S., additional, Hourihane, A., additional, Gilmore, G., additional, Adibekyan, V., additional, Bergemann, M., additional, Cantat-Gaudin, T., additional, Delgado-Mena, E., additional, González Hernández, J. I., additional, Guiglion, G., additional, Lardo, C., additional, de Laverny, P., additional, Lind, K., additional, Magrini, L., additional, Mikolaitis, S., additional, Montes, D., additional, Pancino, E., additional, Recio-Blanco, A., additional, Sordo, R., additional, Sousa, S., additional, Tabernero, H. M., additional, and Vallenari, A., additional

Published
2015
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17. TheGaia-ESO Survey: A globular cluster escapee in the Galactic halo

Author

Lind, K., primary, Koposov, S. E., additional, Battistini, C., additional, Marino, A. F., additional, Ruchti, G., additional, Serenelli, A., additional, Worley, C. C., additional, Alves-Brito, A., additional, Asplund, M., additional, Barklem, P. S., additional, Bensby, T., additional, Bergemann, M., additional, Blanco-Cuaresma, S., additional, Bragaglia, A., additional, Edvardsson, B., additional, Feltzing, S., additional, Gruyters, P., additional, Heiter, U., additional, Jofre, P., additional, Korn, A. J., additional, Nordlander, T., additional, Ryde, N., additional, Soubiran, C., additional, Gilmore, G., additional, Randich, S., additional, Ferguson, A. M. N., additional, Jeffries, R. D., additional, Vallenari, A., additional, Allende Prieto, C., additional, Pancino, E., additional, Recio-Blanco, A., additional, Romano, D., additional, Smiljanic, R., additional, Bellazzini, M., additional, Damiani, F., additional, Hill, V., additional, de Laverny, P., additional, Jackson, R. J., additional, Lardo, C., additional, and Zaggia, S., additional

Published
2015
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18. The Gaia-ESO Survey: The analysis of high-resolution UVES spectra of FGK-type stars

Author

Universidad de Alicante. Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Smiljanic, R., Korn, A., Bergemann, M., Frasca, A., Magrini, L., Masseron, T., Pancino, E., Ruchti, G., San Roman, I., Sbordone, L., Sousa, S.G., Drew, J., Feltzing, S., Ferguson, A., Jeffries, R., Micela, G., Negueruela, Ignacio, Prusti, T., Rix, H.-W., Alfaro, Emilio J., Babusiaux, C., Bensby, T., Blomme, Ronny, Flaccomio, E., Francois, P., Irwin, M., Koposov, S., Walton, N., Bayo, A., Carraro, G., Costado, M.T., Damiani, F., Edvardsson, B., Hourihane, A., Jackson, R.J., Lewis, J., Lind, K., Marconi, G., Martayan, C., Monaco, L., Morbidelli, L., Prisinzano, L., Zaggia, S., Tabernero, Hugo M., Tautvaišienė, G., Valentini, M., Weber, M., Worley, C.C., Adibekyan, V.Zh., Allende Prieto, C., Barisevičius, G., Biazzo, K., Blanco-Cuaresma, S., Bonifacio, P., Bragaglia, A., Caffau, E., Cantat-Gaudin, T., Chorniy, Y., Laverny, P. de, Delgado-Mena, E., Donati, P., Duffau, S., Franciosini, E., Friel, E., Geisler, Douglas, González Hernández, J.I., Gruyters, P., Guiglion, G., Hansen, C.J., Heiter, U., Hill, V., Jacobson, H.R., Jofre, P., Jönsson, H., Lanzafame, A.C., Lardo, C., Ludwig, H.-G., Maiorca, E., Mikolaitis, Š., Montes, David, Morel, Thierry, Mucciarelli, A., Muñoz, C., Nordlander, T., Pasquini, L., Puzeras, E., Recio-Blanco, A., Ryde, N., Sacco, G.G., Santos, N.C., Serenelli, A.M., Sordo, R., Soubiran, C., Spina, L., Steffen, M., Vallenari, A., Van Eck, S., Villanova, S., Gilmore, Gerard, Randich, Sofia, Asplund, M., Binney, J., Universidad de Alicante. Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Smiljanic, R., Korn, A., Bergemann, M., Frasca, A., Magrini, L., Masseron, T., Pancino, E., Ruchti, G., San Roman, I., Sbordone, L., Sousa, S.G., Drew, J., Feltzing, S., Ferguson, A., Jeffries, R., Micela, G., Negueruela, Ignacio, Prusti, T., Rix, H.-W., Alfaro, Emilio J., Babusiaux, C., Bensby, T., Blomme, Ronny, Flaccomio, E., Francois, P., Irwin, M., Koposov, S., Walton, N., Bayo, A., Carraro, G., Costado, M.T., Damiani, F., Edvardsson, B., Hourihane, A., Jackson, R.J., Lewis, J., Lind, K., Marconi, G., Martayan, C., Monaco, L., Morbidelli, L., Prisinzano, L., Zaggia, S., Tabernero, Hugo M., Tautvaišienė, G., Valentini, M., Weber, M., Worley, C.C., Adibekyan, V.Zh., Allende Prieto, C., Barisevičius, G., Biazzo, K., Blanco-Cuaresma, S., Bonifacio, P., Bragaglia, A., Caffau, E., Cantat-Gaudin, T., Chorniy, Y., Laverny, P. de, Delgado-Mena, E., Donati, P., Duffau, S., Franciosini, E., Friel, E., Geisler, Douglas, González Hernández, J.I., Gruyters, P., Guiglion, G., Hansen, C.J., Heiter, U., Hill, V., Jacobson, H.R., Jofre, P., Jönsson, H., Lanzafame, A.C., Lardo, C., Ludwig, H.-G., Maiorca, E., Mikolaitis, Š., Montes, David, Morel, Thierry, Mucciarelli, A., Muñoz, C., Nordlander, T., Pasquini, L., Puzeras, E., Recio-Blanco, A., Ryde, N., Sacco, G.G., Santos, N.C., Serenelli, A.M., Sordo, R., Soubiran, C., Spina, L., Steffen, M., Vallenari, A., Van Eck, S., Villanova, S., Gilmore, Gerard, Randich, Sofia, Asplund, M., and Binney, J.

Abstract

Context. The ongoing Gaia-ESO Public Spectroscopic Survey is using FLAMES at the VLT to obtain high-quality medium-resolution Giraffe spectra for about 105 stars and high-resolution UVES spectra for about 5000 stars. With UVES, the Survey has already observed 1447 FGK-type stars. Aims. These UVES spectra are analyzed in parallel by several state-of-the-art methodologies. Our aim is to present how these analyses were implemented, to discuss their results, and to describe how a final recommended parameter scale is defined. We also discuss the precision (method-to-method dispersion) and accuracy (biases with respect to the reference values) of the final parameters. These results are part of the Gaia-ESO second internal release and will be part of its first public release of advanced data products. Methods. The final parameter scale is tied to the scale defined by the Gaia benchmark stars, a set of stars with fundamental atmospheric parameters. In addition, a set of open and globular clusters is used to evaluate the physical soundness of the results. Each of the implemented methodologies is judged against the benchmark stars to define weights in three different regions of the parameter space. The final recommended results are the weighted medians of those from the individual methods. Results. The recommended results successfully reproduce the atmospheric parameters of the benchmark stars and the expected Teff-log g relation of the calibrating clusters. Atmospheric parameters and abundances have been determined for 1301 FGK-type stars observed with UVES. The median of the method-to-method dispersion of the atmospheric parameters is 55 K for Teff, 0.13 dex for log g and 0.07 dex for [Fe/H]. Systematic biases are estimated to be between 50−100 K for Teff, 0.10−0.25 dex for log g and 0.05−0.10 dex for [Fe/H]. Abundances for 24 elements were derived: C, N, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Mo, Ba, Nd, and Eu. The typical method-to-method

Published
2014

19. The Gaia-ESO Survey: The analysis of high-resolution UVES spectra of FGK-type stars

Author

Naval Postgraduate School (U.S.), Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS), Bragaglia, A., Lanzafame, A.C., Ferguson, A., Frasca, A., Hourihane, A., Serenelli, A.M., Mucciarelli, A., Recio-Blanco, A., Vallenari, A., Bayo, A., Korn, A.J., Edvardsson, B., Allende Prieto, C., Babusiaux, C., Worley, C.C., Hansen, C.J., Lardo, C., Martayan, C., Muñoz, C., Soubiran, C., Geisler, D., Montes, D., Caffau, E., Delgado-Mena, E., Flaccomio. E., Pancino, E., Puzeras, E., Alfaro, E., Franciosini, E., Friel, E., Maiorca, E., Damiani, F., Barisevicius, G., Carraro, G., Gilmore, G., Guiglion, G., Micela, G., Ruchti, G., Sacco, G., Tautvaišien, G., Marconi, G., Rix, H.-W., Jönsson, H., Tabernero, H., Ludwig, H.-G., Jacobson, H.R., Negueruela, I., San Roman, I., Binney, J., González Hernández, J. I., Drew, J., Lewis, J., Biazzo, K., Lind, K, Magrini, L., Monaco, L., Morbidelli, L., Pasquini, L., Prisinzano, L., Sbordone, L., Spina. L., Asplund, M., Bergemann, M., Irwin, M., Valentini, M., Steffen, M., Costado, M.T., Weber, M., Ryde, N., Walton, N., Santos, N.C., Bonifacio, P., Donati, P., Gruyters, P., deLaverny, P., François, P., Jofre, P., Blomme, R., Jackson, R., Smiljanic, R., Jeffries, R., Sordo, R., Blanco-Cuaresma, S., Feltzing, S., Koposov, S., Mikolaitis, Š., Randich, S., Villanova, S., Zaggia, S., Duffau, S., Sousa, S.G., VanEck, S., Bensby, T., Cantat-Gaudin, T., Masseron, T., Nordlander, T., Morel, T., Prusti, T., Heiter, U., Adibekyan, V. Zh., Hill, V., Chorniy, Y., Naval Postgraduate School (U.S.), Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS), Bragaglia, A., Lanzafame, A.C., Ferguson, A., Frasca, A., Hourihane, A., Serenelli, A.M., Mucciarelli, A., Recio-Blanco, A., Vallenari, A., Bayo, A., Korn, A.J., Edvardsson, B., Allende Prieto, C., Babusiaux, C., Worley, C.C., Hansen, C.J., Lardo, C., Martayan, C., Muñoz, C., Soubiran, C., Geisler, D., Montes, D., Caffau, E., Delgado-Mena, E., Flaccomio. E., Pancino, E., Puzeras, E., Alfaro, E., Franciosini, E., Friel, E., Maiorca, E., Damiani, F., Barisevicius, G., Carraro, G., Gilmore, G., Guiglion, G., Micela, G., Ruchti, G., Sacco, G., Tautvaišien, G., Marconi, G., Rix, H.-W., Jönsson, H., Tabernero, H., Ludwig, H.-G., Jacobson, H.R., Negueruela, I., San Roman, I., Binney, J., González Hernández, J. I., Drew, J., Lewis, J., Biazzo, K., Lind, K, Magrini, L., Monaco, L., Morbidelli, L., Pasquini, L., Prisinzano, L., Sbordone, L., Spina. L., Asplund, M., Bergemann, M., Irwin, M., Valentini, M., Steffen, M., Costado, M.T., Weber, M., Ryde, N., Walton, N., Santos, N.C., Bonifacio, P., Donati, P., Gruyters, P., deLaverny, P., François, P., Jofre, P., Blomme, R., Jackson, R., Smiljanic, R., Jeffries, R., Sordo, R., Blanco-Cuaresma, S., Feltzing, S., Koposov, S., Mikolaitis, Š., Randich, S., Villanova, S., Zaggia, S., Duffau, S., Sousa, S.G., VanEck, S., Bensby, T., Cantat-Gaudin, T., Masseron, T., Nordlander, T., Morel, T., Prusti, T., Heiter, U., Adibekyan, V. Zh., Hill, V., and Chorniy, Y.

Abstract

Context. The ongoing Gaia-ESO Public Spectroscopic Survey is using FLAMES at the VLT to obtain high-quality medium-resolution Giraffe spectra for about 10(5) stars and high-resolution UVES spectra for about 5000 stars. With UVES, the Survey has already observed 1447 FGK-type stars. Aims. These UVES spectra are analyzed in parallel by several state-of-the-art methodologies. Our aim is to present how these analyses were implemented, to discuss their results, and to describe how a final recommended parameter scale is defined. We also discuss the precision (method-to-method dispersion) and accuracy (biases with respect to the reference values) of the final parameters. These results are part of the Gaia-ESO second internal release and will be part of its first public release of advanced data products. Methods. The final parameter scale is tied to the scale defined by the Gaia benchmark stars, a set of stars with fundamental atmospheric parameters. In addition, a set of open and globular clusters is used to evaluate the physical soundness of the results. Each of the implemented methodologies is judged against the benchmark stars to define weights in three different regions of the parameter space. The final recommended results are the weighted medians of those from the individual methods. Results. The recommended results successfully reproduce the atmospheric parameters of the benchmark stars and the expected T(eff)-log g relation of the calibrating clusters. Atmospheric parameters and abundances have been determined for 1301 FGK-type stars observed with UVES. The median of the method-to-method dispersion of the atmospheric parameters is 55K for T(eff), 0.13 dex for log g and 0.07 dex for [Fe/H]. Systematic biases are estimated to be between 50−100 K for T(eff), 0.10−0.25 dex for log g and 0.05−0.10 dex for [Fe/H]. Abundances for 24 elements were derived: C, N, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Mo, Ba, Nd, and Eu. The typical method-to-me

Published
2014

20. TheGaia-ESO Survey: The analysis of high-resolution UVES spectra of FGK-type stars

Author

Smiljanic, R., primary, Korn, A. J., additional, Bergemann, M., additional, Frasca, A., additional, Magrini, L., additional, Masseron, T., additional, Pancino, E., additional, Ruchti, G., additional, San Roman, I., additional, Sbordone, L., additional, Sousa, S. G., additional, Tabernero, H., additional, Tautvaišienė, G., additional, Valentini, M., additional, Weber, M., additional, Worley, C. C., additional, Adibekyan, V. Zh., additional, Allende Prieto, C., additional, Barisevičius, G., additional, Biazzo, K., additional, Blanco-Cuaresma, S., additional, Bonifacio, P., additional, Bragaglia, A., additional, Caffau, E., additional, Cantat-Gaudin, T., additional, Chorniy, Y., additional, de Laverny, P., additional, Delgado-Mena, E., additional, Donati, P., additional, Duffau, S., additional, Franciosini, E., additional, Friel, E., additional, Geisler, D., additional, González Hernández, J. I., additional, Gruyters, P., additional, Guiglion, G., additional, Hansen, C. J., additional, Heiter, U., additional, Hill, V., additional, Jacobson, H. R., additional, Jofre, P., additional, Jönsson, H., additional, Lanzafame, A. C., additional, Lardo, C., additional, Ludwig, H.-G., additional, Maiorca, E., additional, Mikolaitis, Š., additional, Montes, D., additional, Morel, T., additional, Mucciarelli, A., additional, Muñoz, C., additional, Nordlander, T., additional, Pasquini, L., additional, Puzeras, E., additional, Recio-Blanco, A., additional, Ryde, N., additional, Sacco, G., additional, Santos, N. C., additional, Serenelli, A. M., additional, Sordo, R., additional, Soubiran, C., additional, Spina, L., additional, Steffen, M., additional, Vallenari, A., additional, Van Eck, S., additional, Villanova, S., additional, Gilmore, G., additional, Randich, S., additional, Asplund, M., additional, Binney, J., additional, Drew, J., additional, Feltzing, S., additional, Ferguson, A., additional, Jeffries, R., additional, Micela, G., additional, Negueruela, I., additional, Prusti, T., additional, Rix, H-W., additional, Alfaro, E., additional, Babusiaux, C., additional, Bensby, T., additional, Blomme, R., additional, Flaccomio, E., additional, François, P., additional, Irwin, M., additional, Koposov, S., additional, Walton, N., additional, Bayo, A., additional, Carraro, G., additional, Costado, M. T., additional, Damiani, F., additional, Edvardsson, B., additional, Hourihane, A., additional, Jackson, R., additional, Lewis, J., additional, Lind, K., additional, Marconi, G., additional, Martayan, C., additional, Monaco, L., additional, Morbidelli, L., additional, Prisinzano, L., additional, and Zaggia, S., additional

Published
2014
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21. TheGaia-ESO Survey: radial metallicity gradients and age-metallicity relation of stars in the Milky Way disk

Author

Bergemann, M., primary, Ruchti, G. R., additional, Serenelli, A., additional, Feltzing, S., additional, Alves-Brito, A., additional, Asplund, M., additional, Bensby, T., additional, Gruiters, P., additional, Heiter, U., additional, Hourihane, A., additional, Korn, A., additional, Lind, K., additional, Marino, A., additional, Jofre, P., additional, Nordlander, T., additional, Ryde, N., additional, Worley, C. C., additional, Gilmore, G., additional, Randich, S., additional, Ferguson, A. M. N., additional, Jeffries, R. D., additional, Micela, G., additional, Negueruela, I., additional, Prusti, T., additional, Rix, H.-W., additional, Vallenari, A., additional, Alfaro, E. J., additional, Allende Prieto, C., additional, Bragaglia, A., additional, Koposov, S. E., additional, Lanzafame, A. C., additional, Pancino, E., additional, Recio-Blanco, A., additional, Smiljanic, R., additional, Walton, N., additional, Costado, M. T., additional, Franciosini, E., additional, Hill, V., additional, Lardo, C., additional, de Laverny, P., additional, Magrini, L., additional, Maiorca, E., additional, Masseron, T., additional, Morbidelli, L., additional, Sacco, G., additional, Kordopatis, G., additional, and Tautvaišienė, G., additional

Published
2014
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22. GaiaFGK benchmark stars: Metallicity

Author

Jofré, P., primary, Heiter, U., additional, Soubiran, C., additional, Blanco-Cuaresma, S., additional, Worley, C. C., additional, Pancino, E., additional, Cantat-Gaudin, T., additional, Magrini, L., additional, Bergemann, M., additional, González Hernández, J. I., additional, Hill, V., additional, Lardo, C., additional, de Laverny, P., additional, Lind, K., additional, Masseron, T., additional, Montes, D., additional, Mucciarelli, A., additional, Nordlander, T., additional, Recio Blanco, A., additional, Sobeck, J., additional, Sordo, R., additional, Sousa, S. G., additional, Tabernero, H., additional, Vallenari, A., additional, and Van Eck, S., additional

Published
2014
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23. 3D NLTE analysis of the most iron-deficient star, SMSS0313-6708.

Author

Nordlander, T., Amarsi, A. M., Lind, K., Asplund, M., Barklem, P. S., Casey, A. R., Collet, R., and Leenaarts, J.

Subjects
*STELLAR evolution, *STELLAR photospheres, *THERMODYNAMIC cycles, *STELLAR spectra, *SUPERNOVAE
Abstract

Context. Models of star formation in the early universe require a detailed understanding of accretion, fragmentation and radiative feedback in metal-free molecular clouds. Different simulations predict different initial mass functions of the first stars, ranging from predominantly low-mass (0.1-10 M⊙ ), to massive (10-100 M⊙ ), or even supermassive (100-1000 M⊙ ). The mass distribution of the first stars should lead to unique chemical imprints on the low-mass second and later generation metal-poor stars still in existence. The chemical composition of SMSS0313-6708, which has the lowest abundances of Ca and Fe of any star known, indicates it was enriched by a single massive supernova. Aims. The photospheres of metal-poor stars are relatively transparent in the UV, which may lead to large three-dimensional (3D) effects as well as departures from local thermodynamical equilibrium (LTE), even for weak spectral lines. If 3D effects and departures from LTE (NLTE) are ignored or treated incorrectly, errors in the inferred abundances may significantly bias the inferred properties of the polluting supernovae. We redetermine the chemical composition of SMSS0313-6708 by means of the most realistic methods available, and compare the results to predicted supernova yields. Methods. A 3D hydrodynamical Stagger model atmosphere and 3D NLTE radiative transfer were applied to obtain accurate abundances for Li, Na, Mg, Al, Ca and Fe. The model atoms employ realistic collisional rates, with no calibrated free parameters. Results. We find significantly higher abundances in 3D NLTE than 1D LTE by 0.8 dex for Fe, and 0.5 dex for Mg, Al and Ca, while Li and Na are unaffected to within 0.03 dex. In particular, our upper limit for [Fe=H] is now a factor ten larger, at [Fe=H] < -6:53 (3σ), than previous estimates based on h3Di NLTE (i.e., using averaged 3D models). This higher estimate is due to a conservative upper limit estimation, updated NLTE data, and 3D-h3Di NLTE differences, all of which lead to a higher abundance determination. Conclusions. We find that supernova yields for models in a wide range of progenitor masses reproduce the revised chemical composition. In addition to massive progenitors of 20-60 M⊙ exploding with low energies (1-2 B, where 1 B = 1051 erg), we also find good fits for progenitors of 10 M⊙, with very low explosion energies (<1 B). We cannot reconcile the new abundances with supernovae or hypernovae with explosion energies above 2.5 B, nor with pair-instability supernovae. [ABSTRACT FROM AUTHOR]

Published
2017
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24. The Gaia-ESO Survey: radial metallicity gradients and age-metallicity relation of stars in the Milky Way disk.

Author

Bergemann, M., Ruchti, G. R., Serenelli, A., Feltzing, S., Alves-Brito, A., Asplund, M., Bensby, T., Gruiters, P., Heiter, U., Hourihane, A., Korn, A., Lind, K., Marino, A., Jofre, P., Nordlander, T., Ryde, N., Worley, C. C., Gilmore, G., Randich, S., and Ferguson, A. M. N.

Subjects
MILKY Way, GALAXY formation, DISTRIBUTION (Probability theory), PLANETARY nebulae, DISKS (Astrophysics), SPECTRUM analysis
Abstract

We study the relationship between age, metallicity, and α-enhancement of FGK stars in the Galactic disk. The results are based upon the analysis of high-resolution UVES spectra from the Gaia-ESO large stellar survey. We explore the limitations of the observed dataset, i.e. the accuracy of stellar parameters and the selection effects that are caused by the photometric target preselection. We find that the colour and magnitude cuts in the survey suppress old metal-rich stars and young metal-poor stars. This suppression may be as high as 97% in some regions of the age-metallicity relationship. The dataset consists of 144 stars with a wide range of ages from 0.5 Gyr to 13.5 Gyr, Galactocentric distances from 6 kpc to 9.5 kpc, and vertical distances from the plane 0 < ∣Z∣ < 1.5 kpc. On this basis, we find that i) the observed age-metallicity relation is nearly flat in the range of ages between 0 Gyr and 8 Gyr; ii) at ages older than 9 Gyr, we see a decrease in [Fe/H] and a clear absence of metal-rich stars; this cannot be explained by the survey selection functions; iii) there is a significant scatter of [Fe/H] at any age; and iv) [Mg/Fe] increases with age, but the dispersion of [Mg/Fe] at ages >9 Gyr is not as small as advocated by some other studies. In agreement with earlier work, we find that radial abundance gradients change as a function of vertical distance from the plane. The [Mg/Fe] gradient steepens and becomes negative. In addition, we show that the inner disk is not only more α-rich compared to the outer disk, but also older, as traced independently by the ages and Mg abundances of stars. [ABSTRACT FROM AUTHOR]

Published
2014
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25. Gaia FGK benchmark stars: Metallicity.

Author

Jofré, P., Heiter, U., Soubiran, C., Blanco-Cuaresma, S., Worley, C. C., Pancino, E., Cantat-Gaudin, T., Magrini, L., Bergemann, M., González Hernández, J. I., Hill, V., Lardo, C., de Laverny, P., Lind, K., Masseron, T., Montes, D., Mucciarelli, A., Nordlander, T., Recio Blanco, A., and Sobeck, J.

Subjects
STAR formation, STELLAR atmospheres, FIELD theory (Physics), ASTRONOMICAL photometry, STELLAR activity
Abstract

Context. To calibrate automatic pipelines that determine atmospheric parameters of stars, one needs a sample of stars, or "benchmark stars", with well-defined parameters to be used as a reference. Aims. We provide detailed documentation of the iron abundance determination of the 34 FGK-type benchmark stars that are selected to be the pillars for calibration of the one billion Gaia stars. They cover a wide range of temperatures, surface gravities, and metallicities. Methods. Up to seven different methods were used to analyze an observed spectral library of high resolutions and high signal-to-noise ratios. The metallicity was determined by assuming a value of effective temperature and surface gravity obtained from fundamental relations, that is, these parameters were known a priori and independently from the spectra. Results. We present a set of metallicity values obtained in a homogeneous way for our sample of benchmark stars. In addition to this value, we provide detailed documentation of the associated uncertainties. Finally, we report a value of the metallicity of the cool giant ψ Phe for the first time. [ABSTRACT FROM AUTHOR]

Published
2014
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26. The Gaia-ESO Survey: A globular cluster escapee in the Galactic halo

Author

Pieter Gruyters, R. D. Jeffries, Carmela Lardo, Sofia Feltzing, Gregory R. Ruchti, Antonella Vallenari, Nils Ryde, Alejandra Recio-Blanco, Caroline Soubiran, Alan Alves-Brito, Maria Bergemann, Anna F. Marino, Martin Asplund, Bengt Edvardsson, Donatella Romano, Aldo Serenelli, Rodolfo Smiljanic, Gerard Gilmore, Thomas Nordlander, Ulrike Heiter, Paul S. Barklem, Annette M. N. Ferguson, S. Blanco-Cuaresma, Paula Jofre, C. Allende Prieto, R. J. Jackson, Angela Bragaglia, Vanessa Hill, Clare Worley, Simone Zaggia, P. de Laverny, Andreas Korn, Sergey E. Koposov, Sofia Randich, Karin Lind, Michele Bellazzini, Francesco Damiani, Elena Pancino, Thomas Bensby, Chiara Battistini, Department of Astronomy and Space Physics [Uppsala], Uppsala University, Dipartimento di Ingegneria industriale e dell'informazione e di economia (DIIIE / UNIVAQ), Università degli Studi dell'Aquila (UNIVAQ), ITA, GBR, FRA, DEU, ESP, SWE, Lind K., Koposov S.E., Battistini C., Marino A.F., Ruchti G., Serenelli A., Worley C.C., Alves-Brito A., Asplund M., Barklem P.S., Bensby T., Bergemann M., Blanco-Cuaresma S., Bragaglia A., Edvardsson B., Feltzing S., Gruyters P., Heiter U., Jofre P., Korn A.J., Nordlander T., Ryde N., Soubiran C., Gilmore G., Randich S., Ferguson A.M.N., Jeffries R.D., Vallenari A., Allende Prieto C., Pancino E., Recio-Blanco A., Romano D., Smiljanic R., Bellazzini M., Damiani F., Hill V., De Laverny P., Jackson R.J., Lardo C., and Zaggia S.

Subjects
Stars: abundance, Population II [stars], Metallicity, Globular clusters: general, FOS: Physical sciences, Techniques: spectroscopic, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Galactic halo, 0103 physical sciences, stellar content [Galaxy], halo [Galaxy], Astrophysics::Solar and Stellar Astrophysics, Omega Centauri, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), general [globular clusters], Astrophysics::Galaxy Astrophysics, QC, QB, Physics, [PHYS]Physics [physics], Galaxy: stellar content, 010308 nuclear & particles physics, Astronomy and Astrophysics, Billion years, Astrophysics - Astrophysics of Galaxies, Galaxy: halo, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], abundances [stars], Red-giant branch, Stars, Astrophysics - Solar and Stellar Astrophysics, Stars: Population II, Space and Planetary Science, Globular cluster, spectroscopic [techniques], Halo, Astrophysics::Earth and Planetary Astrophysics
Abstract

A small fraction of the halo field is made up of stars that share the light element (Z, 4 pages, accepted for publication in Astronomy & Astrophysics

Published
2015
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27. TheGaia-ESO Survey: radial metallicity gradients and age-metallicity relation of stars in the Milky Way disk

Author

M. Bergemann, G. R. Ruchti, A. Serenelli, S. Feltzing, A. Alves-Brito, M. Asplund, T. Bensby, P. Gruiters, U. Heiter, A. Hourihane, A. Korn, K. Lind, A. Marino, P. Jofre, T. Nordlander, N. Ryde, C. C. Worley, G. Gilmore, S. Randich, A. M. N. Ferguson, R. D. Jeffries, G. Micela, I. Negueruela, T. Prusti, H.-W. Rix, A. Vallenari, E. J. Alfaro, C. Allende Prieto, A. Bragaglia, S. E. Koposov, A. C. Lanzafame, E. Pancino, A. Recio-Blanco, R. Smiljanic, N. Walton, M. T. Costado, E. Franciosini, V. Hill, C. Lardo, P. de Laverny, L. Magrini, E. Maiorca, T. Masseron, L. Morbidelli, G. Sacco, G. Kordopatis, G. Tautvaišienė, Universidad de Alicante. Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Astrofísica Estelar (AE), Bergemann M., Ruchti G.R., Serenelli A., Feltzing S., Alves-Brito A., Asplund M., Bensby T., Gruiters P., Heiter U., Hourihane A., Korn A., Lind K., Marino A., Jofre P., Nordlander T., Ryde N., Worley C.C., Gilmore G., Randich S., Ferguson A.M.N., Jeffries R.D., Micela G., Negueruela I., Prusti T., Rix H.-W., Vallenari A., Alfaro E.J., Allende Prieto C., Bragaglia A., Koposov S.E., Lanzafame A.C., Pancino E., Recio-Blanco A., Smiljanic R., Walton N., Costado M.T., Franciosini E., Hill V., Lardo C., De Laverny P., Magrini L., Maiorca E., Masseron T., Morbidelli L., Sacco G., Kordopatis G., and Tautvaisiene G.

Subjects
Solar neighborhood, Milky Way, Metallicity, Formation, FOS: Physical sciences, Galaxia, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Surveys, fundamental parameters [Stars], Astronomia ultravioleta, 01 natural sciences, Spectral line, Galaxy: disk, Stars:fundamental parameter, Fundamental parameters, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Abundances, Disc, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Astronomía y Astrofísica, Mapeamentos astronômicos, Physics, 010308 nuclear & particles physics, Plane (geometry), Stars:abundance, Vertical distance, Astronomy and Astrophysics, Composicao estelar, Astrophysics - Astrophysics of Galaxies, Espectros estelares, Stars, Galaxy, formation [Galaxy], Galaxy: formation, Disk, Space and Planetary Science, abundances [Stars], Astrophysics of Galaxies (astro-ph.GA), Magnitude (astronomy), Astrophysics::Earth and Planetary Astrophysics, disk [Galaxy]
Abstract

We study the relationship between age, metallicity, and alpha-enhancement of FGK stars in the Galactic disk. The results are based upon the analysis of high-resolution UVES spectra from the Gaia-ESO large stellar survey. We explore the limitations of the observed dataset, i.e. the accuracy of stellar parameters and the selection effects that are caused by the photometric target preselection. We find that the colour and magnitude cuts in the survey suppress old metal-rich stars and young metal-poor stars. This suppression may be as high as 97% in some regions of the age-metallicity relationship. The dataset consists of 144 stars with a wide range of ages from 0.5 Gyr to 13.5 Gyr, Galactocentric distances from 6 kpc to 9.5 kpc, and vertical distances from the plane 0 < |Z| < 1.5 kpc. On this basis, we find that i) the observed age-metallicity relation is nearly flat in the range of ages between 0 Gyr and 8 Gyr; ii) at ages older than 9 Gyr, we see a decrease in [Fe/H] and a clear absence of metal-rich stars; this cannot be explained by the survey selection functions; iii) there is a significant scatter of [Fe/H] at any age; and iv) [Mg/Fe] increases with age, but the dispersion of [Mg/Fe] at ages > 9 Gyr is not as small as advocated by some other studies. In agreement with earlier work, we find that radial abundance gradients change as a function of vertical distance from the plane. The [Mg/Fe] gradient steepens and becomes negative. In addition, we show that the inner disk is not only more alpha-rich compared to the outer disk, but also older, as traced independently by the ages and Mg abundances of stars., accepted for publication in A&A

Published
2014
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