Model atmosphere analysis of high-dispersion spectra of four red giants and supergiants.

A model atmosphere analysis of three cool giants (β Cet, α Tau, α TrA) and one supergiant (ɛ Peg) is presented. One of the principal reasons for the analysis being the search for possible non-LTE effects, the measured lines are split into high excitation lines and low excitation lines in order to test the sensitivity of the ionization balance method against deviations from LTE. Even though for iron no pronounced split can be found to occur, other elements, e.g. Mn and Ni, hint at the existence of deviations from LTE in cool giant stars. Deviations from the solar abundance pattern are found for the elements of medium atomic number. Two of the stars (α TrA and ɛ Peg) display over-abundances in barium.