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Issue A&A
Volume 367, Number 3, March I 2001
Page(s) 831 - 839
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20000531



A&A 367, 831-839 (2001)
DOI: 10.1051/0004-6361:20000531

Spectroscopic investigations of classical Cepheids and main-sequence stars in galactic open clusters and associations

I. Association Cas OB2 and the small-amplitude Cepheid SU Cassiopeae
I. A. Usenko1, 2, V. V. Kovtyukh1, 2, V. G. Klochkova3, 4, V. E. Panchuk3, 4 and S. V. Yermakov3

1  Astronomical Observatory of Odessa State University, Odessa 65014, Ukraine
    e-mail: val@deneb.odessa.ua
2  Isaac Newton Institute of Chile, Odessa Branch
3  Special Astrophysical Observatory, Russian Academy of Sciences, Nizhny Arkhyz, Stavropol Territory, 369167, Russia
    e-mail: valenta@sao.ru; panchuk@sao.ru; ermak@sao.ru
4  Isaac Newton Institute of Chile, SAO RAS Branch

(Received 13 July 2000 / Accepted 17 November 2000)

Abstract
The small-amplitude Cepheid SU Cas and four members of the association Cas OB2 (HD 16893, HD 17327a and b , HD 17443) were investigated, using high-resolution CCD spectra. The following results were obtained: 1) All these objects have the same metallicity values, close to that of the Sun; 2) Elemental abundance indicates that SU Cas is a post first dredge-up star with an age from 1 108 to 1.45 108 yr, and it is not crossing the Cepheid instability strip for the first time. The mean value of $\log g$ = 2.35 corresponds to pulsations in the fundamental tone, although errors in gravity estimations provide overtone pulsations. The questions about its pulsational mode and membership in Cas OB2 remained open; 3) HD 17327a is a slowly rotating HgMn-star with the highest helium content among such objects, while HD 16893 also has a manganese overabundance and might be classified as an Am-star; 4) HD 17327b and HD 17443 are rapidly rotating main-sequence stars, while HD 17443 has a helium content comparable with that of the Sun.


Key words: associations -- stars: abundances -- stars: Cepheids -- stars: main-sequence

Offprint request: I. A. Usenko, igus@deneb.odessa.ua

SIMBAD Objects in preparation



© ESO 2001


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