A&A 599, A128 (2017) Astronomy DOI: 10.1051/0004-6361/201629306 & c ESO 2017 Astrophysics Three-dimensional hydrodynamical CO5BOLD model atmospheres of red giant stars V. Oxygen abundance in the metal-poor giant HD 122563 from OH UV lines D. Prakapaviciusˇ 1, A. Kucinskasˇ 1; 2, V.Dobrovolskas1, J. Klevas1, M. Steffen3; 4, P.Bonifacio4, H.-G. Ludwig4; 5, and M. Spite4 1 Institute of Theoretical Physics and Astronomy, Vilnius University, Sauletekio˙ al. 5, 10221 Vilnius, Lithuania e-mail:
[email protected] 2 Astronomical Observatory, Vilnius University, M. K. Ciurlionioˇ 29, 03100 Vilnius, Lithuania 3 Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany 4 GEPI, Observatoire de Paris, CNRS, Université Paris Diderot, Place Jules Janssen, 92190 Meudon, France 5 Landessternwarte – Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany Received 13 July 2016 / Accepted 9 November 2016 ABSTRACT Context. Although oxygen is an important tracer of the early Galactic evolution, its abundance trends with metallicity are still rela- tively poorly known at [Fe=H] . −2:5. This is in part due to a lack of reliable oxygen abundance indicators in the metal-poor stars, and in part due to shortcomings in 1D LTE abundance analyses where different abundance indicators, such as OH lines located in the UV and IR or the forbidden [O I] line at 630 nm, frequently provide inconsistent results. Aims. In this study, we determined the oxygen abundance in the metal-poor halo giant HD 122563 using a 3D hydrodynamical CO5BOLD model atmosphere. Our main goal was to understand whether a 3D LTE analysis can help to improve the reliability of oxygen abundances that are determined from OH UV lines in comparison to those obtained using standard 1D LTE methodology.