Eu III identification and Eu abundance in CP stars
Abstract
We report the first identification of the Eu iii lambda 6666.347 line in optical spectra of CP stars. This line is clearly present in the spectra of HR 4816, 73 Dra, HR 7575, beta CrB, and alpha (2) CVn, while it is marginally present or absent in spectra of the roAp stars (rapidly oscillating Ap stars, cf. Kurtz 1990) alpha Cir, gamma Equ, HD 203932, GZ Lib (33 Lib), and HD 24712. Careful synthetic spectrum calculations for the Eu ii lambda 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 log (gf)=1.18 +/- 0.14 for the Eu iii lambda 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 lambda lambda 7221.838, 7225.151, and 8079.071.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 1999
- Bibcode:
- 1999A&A...343..229R
- Keywords:
-
- ATOMIC DATA;
- STARS: ABUNDANCES;
- STARS: CHEMICALLY PECULIAR;
- STARS: MAGNETIC FIELDS