Astron. Astrophys. 351, 597-606 (1999)

Do we really obtain reliable elemental abundances for supergiant stars?  ^*

V.V. Kovtyukh and S.M. Andrievsky

Department of Astronomy, Odessa State University, Shevchenko Park, 270014 Odessa, Ukraine (scan@deneb.odessa.ua)

Received 31 May 1999 / Accepted 31 August 1999

Abstract

We discuss the problems of standard spectroscopic analysis of intermediate mass supergiants and propose the usage of lines for the microturbulent velocity and gravity determination, instead of lines that are usually applied for this aim, but more affected by non-LTE effects.

With the example of Cep (seven high-resolution and high signal-to-noise ratio spectra) we demonstrate that the proposed approach results in the following advantages:

• it removes the long-standing problem of the discrepancy between the spectroscopic and physical gravities (based on the estimated stellar masses and radii), resulting in a complete agreement between these values;

• it brings the abundances of some elements (among them carbon, nitrogen, oxygen) in accordance with the theoretically predicted atmospheric abundances for the supergiants of intermediate masses after the first dredge-up phase;

• it allows us to keep an ionization balance of some elements observed in two ionizational stages together with the balance.

Key words: stars: abundances stars: individual: ffi Cep stars: variables: Cepheids

* The Appendix is only available electronically with the On-Line publication.

Send offprint requests to: S.M. Andrievsky

© European Southern Observatory (ESO) 1999

Online publication: November 3, 1999

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