Astronomy and Astrophysics, volume 343, 229-236 (1999/3-1)
Eu III identification and Eu abundance in CP stars.
RYABCHIKOVA T., PISKUNOV N., SAVANOV I., KUPKA F. and MALANUSHENKO V.
Abstract (from CDS):
We report the first identification of the EuIII λ 6666.347 line in optical spectra of CP stars. This line is clearly present in the spectra of HR 4816, 73 Dra, HR 7575, β CrB, and α2
CVn, while it is marginally present or absent in spectra of the roAp stars (rapidly oscillating Ap stars, cf. Kurtz, 1990ARA&A..28..607K
) α Cir, γ Equ, HD 203932, GZ Lib (33 Lib), and HD 24712. Careful synthetic spectrum calculations for the EuII λ 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 EuII lines. Assuming an ionization balance in the stellar atmospheres we give an estimate of the astrophysical oscillator strength log(gf)=1.18±0.14 for the EuIII λ 6666.347 line. This value is obtained without taking into account a possible hyperfine-splitting which is unknown for this EuIII line. We also provide astrophysical gf-values for EuIII λλ 7221.838, 7225.151, and 8079.071.
atomic data - stars: abundances - stars: chemically peculiar - stars: magnetic fields
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