We discuss the problems of standard spectroscopic analysis of intermediate
mass supergiants and propose the usage of Fe II lines for the microturbulen
t velocity and gravity determination, instead of Fe I lines that are usuall
y applied for this aim, but more affected by non-LTE effects.
With the example of delta Cep (seven high-resolution and high signal-to-noi
se ratio spectra) we demonstrate that the proposed approach results in the
following advantages:
1 it removes the long-standing problem of the discrepancy between the spect
roscopic and physical gravities (based on the estimated stellar masses and
radii), resulting in a complete agreement between these values;
2 it brings the abundances of some elements (among them carbon, nitrogen, o
xygen) in accordance with the theoretically predicted atmospheric abundance
s for the supergiants of intermediate masses after the first dredge-up phas
e;
3 it allows us to keep an ionization balance of some elements observed in t
wo ionizational stages together with the Fe I/Fe II balance.