Andreas J. Korn

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We report on a dedicated effort to identify and study metal-poor stars strongly enhanced in r-process elements ([r/Fe]> 1 dex; hereafter r-II stars), the Hamburg/ESO R-process Enhanced Star survey (HERES). Moderate-resolution (∼ 2 Å) follow-up spectroscopy has been obtained for metal-poor giant candidates selected from the Hamburg/ESO objective-prism survey(More)
Non-LTE line formation calculations of Fe  are performed for a small number of reference stars to investigate and quantify the efficiency of neutral hydrogen collisions. Using the atomic model that was described in previous publications, the final discrimination with respect to hydrogen collisions is based on the condition that the surface gravities as(More)
Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7. Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the(More)
Context. The Gaia-ESO Public Spectroscopic Survey is obtaining high-quality spectroscopy of some 100 000 Milky Way stars using the FLAMES spectrograph at the VLT, down to V = 19 mag, systematically covering all the main components of the Milky Way and providing the first homogeneous overview of the distributions of kinematics and chemical element abundances(More)
NLTE line formation calculations of Fe I in the solar atmosphere are extended to include weak lines in the visual spectrum of the Sun. Previously established atomic models are used to discriminate between different ways of treating collisional interaction processes. As indicated by the analysis of strong Fe I lines, the influence of deviations from LTE in(More)
We present the first results of the EMBLA survey (Extremely Metal-poor BuLge stars with AAOmega), aimed at finding metal-poor stars in the Milky Way bulge, where the oldest stars should now preferentially reside. EMBLA utilizes SkyMapper photometry to pre-select metal-poor candidates, which are subsequently confirmed using AAOmega spectroscopy. We describe(More)
  • E. Pancino, C. Lardo, +10 authors A. C. Lanzafame
  • 2016
The Gaia-ESO survey (GES) is now in its fifth and last year of observations, and has already produced tens of thousands of high-quality spectra of stars in all Milky Way components. This paper presents the strategy behind the selection of astrophysical calibration targets, ensuring that all GES results on radial velocities, atmospheric parameters, and(More)