Volume 415, Number 1, February III 2004
|Page(s)||273 - 282|
|Section||Stellar structure and evolution|
|Published online||03 February 2004|
Tartu Observatory, 61602, Tõravere, Estonia
2 Department of Physics, University of Tartu, 4 Tähe Street, 50090, Tartu, Estonia
3 Uniwersytet Mikołaja Kopernika, Centrum Astronomii, ul. Gagarina 11, 87-100, Toruń, Poland
Corresponding author: L. Leedjärv, email@example.com
Accepted: 9 October 2003
The halo symbiotic star AG Dra has been monitored spectroscopically at the Tartu Observatory, Estonia, from September 1997 to March 2003. Altogether 189 spectra are used in the present paper. In addition, photometric UBVri observations at the Piwnice Observatory, Poland, from March 1996 to May 2003 are presented. Equivalent widths () of the strongest emission lines (Hα, Hβ, λ 4686, Raman scattered λ 6825) appear to be strongly variable, and in general, correlate with the U brightness of the star. No apparent correlation with the orbital motion of the binary system was found, except for Hβ in the quiescent state. At the same time, there is a clear convergence of the high values of to certain phases according to the shorter photometric period (378.5 days) proposed by Bastian (1998) and the pulsational period of the cool giant (355.27 days) by Gális et al. (1999). Higher resolution spectra show variability of the Hα profiles, with weak absorption component on the blue wing of the line around photometric minimum if the star is in quiescent state. The significant role of the cool giant in the activity of AG Dra is discussed.
Key words: stars: binaries: symbiotic / stars: winds, outflows / stars: individual: AG Dra
© ESO, 2004
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