Browsing by Author "Zwitter, T."
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- ItemThe Gaia-ESO Survey: Extracting diffuse interstellar bands from cool star spectra DIB-based interstellar medium line-of-sight structures at the kpc scale(EDP SCIENCES S A, 2015) Puspitarini, L.; Lallement, R.; Babusiaux, C.; Chen, H. C.; Bonifacio, P.; Sbordone, L.; Caffau, E.; Duffau, S.; Hill, V.; Monreal Ibero, A.; Royer, F.; Arenou, F.; Peralta, R.; Drew, J. E.; Bonito, R.; Lopez Santiago, J.; Alfaro, E. J.; Bensby, T.; Bragaglia, A.; Flaccomio, E.; Lanzafame, A. C.; Pancino, E.; Recio Blanco, A.; Smiljanic, R.; Costado, M. T.; Lardo, C.; de Laverny, P.; Zwitter, T.Aims. We study how diffuse interstellar bands (DIBs) measured toward distance-distributed target stars can be used to locate dense interstellar (IS) clouds in the Galaxy and probe a line-of-sight (LOS) kinematical structure, a potentially useful tool when gaseous absorption lines are saturated or not available in the spectral range. Cool target stars are numerous enough for this purpose.
- ItemThe Gaia-ESO Survey: revisiting the Li-rich giant problem(OXFORD UNIV PRESS, 2016) Casey, A. R.; Ruchti, G.; Masseron, T.; Randich, S.; Gilmore, G.; Lind, K.; Kennedy, G. M.; Koposov, S. E.; Hourihane, A.; Franciosini, E.; Lewis, J. R.; Magrini, L.; Morbidelli, L.; Sacco, G. G.; Worley, C. C.; Feltzing, S.; Jeffries, R. D.; Vallenari, A.; Bensby, T.; Bragaglia, A.; Flaccomio, E.; Francois, P.; Korn, A. J.; Lanzafame, A.; Pancino, E.; Recio Blanco, A.; Smiljanic, R.; Carraro, G.; Costado, M. T.; Damiani, F.; Donati, P.; Frasca, A.; Jofre, P.; Lardo, C.; de Laverny, P.; Monaco, L.; Prisinzano, L.; Sbordone, L.; Sousa, S. G.; Tautvaisiene, G.; Zaggia, S.; Zwitter, T.; Delgado Mena, E.; Chorniy, Y.; Martell, S. L.; Aguirre, V. Silva; Miglio, A.; Chiappini, C.; Montalban, J.; Morel, T.; Valentini, M.The discovery of lithium-rich giants contradicts expectations from canonical stellar evolution. Here we report on the serendipitous discovery of 20 Li-rich giants observed during the Gaia-ESO Survey, which includes the first nine Li-rich giant stars known towards the CoRoT fields. Most of our Li-rich giants have near-solar metallicities and stellar parameters consistent with being before the luminosity bump. This is difficult to reconcile with deep mixing models proposed to explain lithium enrichment, because these models can only operate at later evolutionary stages: at or past the luminosity bump. In an effort to shed light on the Li-rich phenomenon, we highlight recent evidence of the tidal destruction of close-in hot Jupiters at the sub-giant phase. We note that when coupled with models of planet accretion, the observed destruction of hot Jupiters actually predicts the existence of Li-rich giant stars, and suggests that Li-rich stars should be found early on the giant branch and occur more frequently with increasing metallicity. A comprehensive review of all known Li-rich giant stars reveals that this scenario is consistent with the data. However, more evolved or metal-poor stars are less likely to host close-in giant planets, implying that their Li-rich origin requires an alternative explanation, likely related to mixing scenarios rather than external phenomena.
- ItemThe Gaia-ESO Survey: the selection function of the Milky Way field stars(OXFORD UNIV PRESS, 2016) Stonkute, E.; Koposov, S. E.; Howes, L. M.; Feltzing, S.; Worley, C. C.; Gilmore, G.; Ruchti, G. R.; Kordopatis, G.; Randich, S.; Zwitter, T.; Bensby, T.; Bragaglia, A.; Smiljanic, R.; Costado, M. T.; Tautvaisiene, G.; Casey, A. R.; Korn, A. J.; Lanzafame, A. C.; Pancino, E.; Franciosini, E.; Hourihane, A.; Jofre, P.; Lardo, C.; Lewis, J.; Magrini, L.; Monaco, L.; Morbidelli, L.; Sacco, G. G.; Sbordone, L.The Gaia-ESO Survey was designed to target all major Galactic components (i.e. bulge, thin and thick discs, halo and clusters), with the goal of constraining the chemical and dynamical evolution of the Milky Way. This paper presents the methodology and considerations that drive the selection of the targeted, allocated and successfully observed Milky Way field stars. The detailed understanding of the survey construction, specifically the influence of target selection criteria on observed Milky Way field stars is required in order to analyse and interpret the survey data correctly. We present the target selection process for the Milky Way field stars observed with Very Large Telescope/Fibre Large Array Multi Element Spectrograph and provide the weights that characterize the survey target selection. The weights can be used to account for the selection effects in the Gaia-ESO Survey data for scientific studies. We provide a couple of simple examples to highlight the necessity of including such information in studies of the stellar populations in the Milky Way.