The outer atmospheres of the 'hybrid' bright giants : the chromospheres of alpha TrA (K4 II), IOTA AUR (K3 II), gamma AQL (K3 II) , and theta HER (K1 II).

Abstract

Detailed models of the chromospheres of several 'hybrid' bright giants are presented. The models extend from the base of the chromosphere and into the transition area. These chromospheric models are based on radiative transfer calculations for a range of atoms and emission lines. The presence of steep turbulent velocity gradients leads to profiles of optically thin chromospheric emission lines that are heavily dependent on the distribution of emitting material with temperature.