Astronomy and Astrophysics – Astrophysics
Scientific paper
Jan 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996a%26a...305..325k&link_type=abstract
Astronomy and Astrophysics, v.305, p.325
Astronomy and Astrophysics
Astrophysics
35
Atomic Data, Line: Formation, Sun: Abundances, Stars: Abundances
Scientific paper
Determinations of the solar iron abundance have converged to the meteoritic value with the FeII studies of Holweger et al. (1990), Biemont et al. (1991) and Hannaford et al. (1992) and the FeI results of Holweger et al. (1991). However, the latter authors pointed out that Blackwell et al. (1984) obtained a discordant result from similar oscillator strengths. A recent debate on this lingering discrepancy by the Oxford and Kiel contenders themselves has not clarified the issue. We do so here by showing that it stems from systematic differences between equivalent widths and oscillator strengths which masquerade as difference in fitted damping enhancement factors. We first discuss the various error sources in classical abundance determination and then emulate both sides of the debate with abundance fits of our own. Our emulation of the Oxford side shows that the abundance anomaly claimed by Blackwell et al. (1984) for solar FeI 2.2eV lines vanishes when equivalent width measurements from other authors are combined with better evaluation of the collisional damping parameter. On the Kiel side, we find that the oscillator strengths of Bard et al. (1991) used by Holweger et al. (1991) produce a suspicious trend when used to fit solar FeI lines, whereas comparable application of oscillator strengths from Oxford does not. The trend is mainly set by categories of FeI lines not measured at Oxford; for lines of overlap the two sets agree and deliver the iron abundance value A_Fe_=7.62+/-0.04 which exceeds the meteorite value. The dissimilar lines may suffer from solar line-formation effects. We conclude that the issue of the solar iron abundance remains open. Definitive oscillator strengths are still needed, as well as verification of classical abundance determination by more realistic representations of the solar photosphere and of photospheric line formation.
Kostik Roman I.
Rutten Robert J.
Shchukina Nataliya G.
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