Astron. Astrophys. 343, 229-236 (1999)

Eu III identification and Eu abundance in CP stars

T. Ryabchikova ¹, N. Piskunov ², I. Savanov ^3,4, F. Kupka ⁵ and V. Malanushenko <sup>3,4

1</sup> Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya str. 48, 109017 Moscow, Russia (e-mail: ryabchik@inasan.rssi.ru)
² Uppsala Astronomical Observatory, Box 515, S-751 20 Uppsala, Sweden (e-mail: piskunov@nils.astro.uu.se)
³ Crimean Astrophysical Observatory
⁴ Isaac Newton Institute of Chile, Crimean Branch, 334413 Nauchny, Crimea, Ukraine (e-mail: savanov@crao.crimea.ua)
⁵ Institute for Astronomy, University of Vienna, Türkenschanzstrasse 17, A-1180 Vienna, Austria (e-mail: kupka@galileo.astro.univie.ac.at)

Received 26 June 1998 / Accepted 4 December 1998

Abstract

We report the first identification of the Eu III 6666.347 line in optical spectra of CP stars. This line is clearly present in the spectra of HR 4816, 73 Dra, HR 7575, CrB, and CVn, while it is marginally present or absent in spectra of the roAp stars (rapidly oscillating Ap stars, cf. Kurtz 1990) Cir, Equ, HD 203932, GZ Lib (33 Lib), and HD 24712.

Careful synthetic spectrum calculations for the Eu II 6645.11 line taking into account hyperfine, isotopic, and magnetic splittings allow us to obtain more accurate Eu abundances in the atmospheres of 9 CP stars. In most cases the derived abundances are significantly lower than the previous results reported for some of the stars based on coarse analysis of the famous blue Eu II lines. Assuming an ionization balance in the stellar atmospheres we give an estimate of the astrophysical oscillator strength =1.18 0.14 for the Eu III 6666.347 line. This value is obtained without taking into account a possible hyperfine-splitting which is unknown for this Eu III line. We also provide astrophysical gf-values for Eu III 7221.838, 7225.151, and 8079.071.

Key words: atomic data stars: abundances stars: chemically peculiar stars: magnetic fields

Send offprint requests to: F. Kupka

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Contents

• 1. Introduction
• 2. Observations
• 3. Identification of the Eu III 6666.347 line
• 4. Method of the analysis
  • 4.1. Parameter determination
  • 4.2. Spectrum synthesis for magnetic stars
• 5. Results
  • 5.1. Cool stars
  • 5.2. CVn
• 6. Discussion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999
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