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Centro de Astrofísica da Universidade do Porto

Another forbidden solar oxygen abundance: the [OI] 5577 Å line

J. Meléndez, M. Asplund

Context. Recent works with improved model atmospheres, line formation, atomic and  molecular data, and detailed treatment of blends, have resulted in a significant  downward revision of the solar oxygen abundance.
Aims. Considering the importance of the Sun as an astrophysical standard and the  current conflict of standard solar models using the new solar abundances with  helioseismological observations we have performed a new study of the solar oxygen  abundance based on the forbidden [OI] line at 5577.34 Å, not previously considered.
High-resolution (R > 500 000), high signal-to-noise (S/N > 1000) solar  spectra of the [OI] 5577.34 Å line have been analyzed employing both three dimensional (3D) and a variety of 1D (spatially and temporally averaged 3D, Holweger  & Müller, MARCS and Kurucz models with and without convective overshooting) model atmospheres.
Results. The oxygen abundance obtained from the [OI] 5577.3 Å forbidden line is  almost insensitive to the input model atmosphere and has a mean value of log εo =  8.71 ± 0.02 (σ from using the different model atmospheres). The total error (0.07  dex) is dominated by uncertainties in the log gf value (0.03 dex), apparent line variation (0.04 dex) and uncertainties in the continuum and line positions (0.05 dex).
Conclusions. The here derived oxygen abundance is close to the 3D-based estimates  from the two other [OI] lines at 6300 and 6363 Å, the permitted OI lines and vibrational and rotational OH transitions in the infrared. Our study thus supports a low  solar oxygen abundance (log εo ≈ 8.7), independent of the adopted model  atmosphere.

Astronomy and Astrophysics
Volume 490, Page 817
November 2008

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