Do we really obtain reliable elemental abundances for supergiant stars?

Citation
Vv. Kovtyukh et Sm. Andrievsky, Do we really obtain reliable elemental abundances for supergiant stars?, ASTRON ASTR, 351(2), 1999, pp. 597-606
Citations number
38
Categorie Soggetti
Space Sciences
Journal title
ASTRONOMY AND ASTROPHYSICS
ISSN journal
00046361 → ACNP
Volume
351
Issue
2
Year of publication
1999
Pages
597 - 606
Database
ISI
SICI code
0004-6361(199911)351:2<597:DWRORE>2.0.ZU;2-K
Abstract
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.