Norbert Przybilla (Dr. Remeis Observatory Bamberg/Univ. Erlangen-Nuremberg, Germany)
A-type supergiants are among the visually brightest stars in galaxies. With the current generation of instrumentation high-resolution spectroscopy of individual supergiant stars is feasible throughout the galaxies of the Local Group, and at intermediate resolution out to several megaparsec distance. Therefore, absorption-line studies of A-type supergiants provide an important complement to the objects traditionally used for oxygen abundance determinations in other galaxies, gaseous nebulae. They can serve to verify and calibrate the strong-line methods employed in emission-line studies. I will introduce the indicators available in the optical and near-IR spectra of A-type supergiants for quantitative analyses, discuss open and solved issues of the required non-LTE modelling, and the accuracy and precision to which oxygen abundances can be derived in this objects. The results obtained so far in terms of Galactic and extragalactic applications will be briefly reviewed.
Invited talk given at the meeting Mapping Oxygen in the Universe, Tenerife, Spain (14-18 May 2012)
