Metal-Rich A-Type Supergiants in M31

Abstract

We discuss results of an exploratory non-LTE analysis of two metal-rich A-type supergiants in M31. Using comprehensive model atoms we derive accurate atmospheric parameters from multiple indicators and show that non-LTE effects on the abundance determination can be substantial (by a factor 2-3). The non-LTE analysis removes systematic trends apparent in the LTE approach and reduces statistical uncertainties. Characteristic abundance patterns of the light elements provide empirical constraints on the evolution of metal-rich massive stars.