The photospheric solar oxygen project II. Non-concordance of the oxygen abundance derived from two forbidden lines

E. Caffau, H. G. Ludwig, J. M. Malherbe, P. Bonifacio, M. Steffen, L. Monaco

Resultado de la investigación: Article

10 Citas (Scopus)

Resumen

Context. In the Sun, the two forbidden [O i] lines at 630 and 636 nm were previously found to provide discrepant oxygen abundances. Aims. We investigate whether this discrepancy is peculiar to the Sun or whether it is also observed in other stars. Methods. We make use of high-resolution, high signal-to-noise ratio spectra of four dwarf to turn-off stars, five giant stars, and one sub-giant star observed with THEMIS, HARPS, and UVES to investigate the coherence of the two lines. Results. The two lines provide oxygen abundances that are consistent, within observational errors, in all the giant stars examined by us. On the other hand, for the two dwarf stars for which a measurement was possible, for Procyon, and for the sub-giant star Capella, the 636 nm line provides systematically higher oxygen abundances, as already seen for the Sun. Conclusions. The only two possible reasons for the discrepancy are a serious error in the oscillator strength of the Ni i line blending the 630 nm line or the presence of an unknown blend in the 636 nm line, which makes the feature stronger. The CN lines blending the 636 nm line cannot be responsible for the discrepancy. The Ca i autoionisation line, on the red wing of which the 636 nm line is formed, is not well modelled by our synthetic spectra. However, a better reproduction of this line would result in even higher abundances from the 636 nm, thus increasing the discrepancy.

Idioma originalEnglish
Número de artículoA126
PublicaciónAstronomy and Astrophysics
Volumen554
DOI
EstadoPublished - 2013

Huella dactilar

giant stars
oxygen
sun
dwarf stars
stars
autoionization
wings
oscillator strengths
signal-to-noise ratio
signal to noise ratios
project
high resolution

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Citar esto

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title = "The photospheric solar oxygen project II. Non-concordance of the oxygen abundance derived from two forbidden lines",
abstract = "Context. In the Sun, the two forbidden [O i] lines at 630 and 636 nm were previously found to provide discrepant oxygen abundances. Aims. We investigate whether this discrepancy is peculiar to the Sun or whether it is also observed in other stars. Methods. We make use of high-resolution, high signal-to-noise ratio spectra of four dwarf to turn-off stars, five giant stars, and one sub-giant star observed with THEMIS, HARPS, and UVES to investigate the coherence of the two lines. Results. The two lines provide oxygen abundances that are consistent, within observational errors, in all the giant stars examined by us. On the other hand, for the two dwarf stars for which a measurement was possible, for Procyon, and for the sub-giant star Capella, the 636 nm line provides systematically higher oxygen abundances, as already seen for the Sun. Conclusions. The only two possible reasons for the discrepancy are a serious error in the oscillator strength of the Ni i line blending the 630 nm line or the presence of an unknown blend in the 636 nm line, which makes the feature stronger. The CN lines blending the 636 nm line cannot be responsible for the discrepancy. The Ca i autoionisation line, on the red wing of which the 636 nm line is formed, is not well modelled by our synthetic spectra. However, a better reproduction of this line would result in even higher abundances from the 636 nm, thus increasing the discrepancy.",
keywords = "Line: formation, Radiative transfer, Stars: abundances, Sun: abundances, Sun: photosphere",
author = "E. Caffau and Ludwig, {H. G.} and Malherbe, {J. M.} and P. Bonifacio and M. Steffen and L. Monaco",
year = "2013",
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The photospheric solar oxygen project II. Non-concordance of the oxygen abundance derived from two forbidden lines. / Caffau, E.; Ludwig, H. G.; Malherbe, J. M.; Bonifacio, P.; Steffen, M.; Monaco, L.

En: Astronomy and Astrophysics, Vol. 554, A126, 2013.

Resultado de la investigación: Article

TY - JOUR

T1 - The photospheric solar oxygen project II. Non-concordance of the oxygen abundance derived from two forbidden lines

AU - Caffau, E.

AU - Ludwig, H. G.

AU - Malherbe, J. M.

AU - Bonifacio, P.

AU - Steffen, M.

AU - Monaco, L.

PY - 2013

Y1 - 2013

N2 - Context. In the Sun, the two forbidden [O i] lines at 630 and 636 nm were previously found to provide discrepant oxygen abundances. Aims. We investigate whether this discrepancy is peculiar to the Sun or whether it is also observed in other stars. Methods. We make use of high-resolution, high signal-to-noise ratio spectra of four dwarf to turn-off stars, five giant stars, and one sub-giant star observed with THEMIS, HARPS, and UVES to investigate the coherence of the two lines. Results. The two lines provide oxygen abundances that are consistent, within observational errors, in all the giant stars examined by us. On the other hand, for the two dwarf stars for which a measurement was possible, for Procyon, and for the sub-giant star Capella, the 636 nm line provides systematically higher oxygen abundances, as already seen for the Sun. Conclusions. The only two possible reasons for the discrepancy are a serious error in the oscillator strength of the Ni i line blending the 630 nm line or the presence of an unknown blend in the 636 nm line, which makes the feature stronger. The CN lines blending the 636 nm line cannot be responsible for the discrepancy. The Ca i autoionisation line, on the red wing of which the 636 nm line is formed, is not well modelled by our synthetic spectra. However, a better reproduction of this line would result in even higher abundances from the 636 nm, thus increasing the discrepancy.

AB - Context. In the Sun, the two forbidden [O i] lines at 630 and 636 nm were previously found to provide discrepant oxygen abundances. Aims. We investigate whether this discrepancy is peculiar to the Sun or whether it is also observed in other stars. Methods. We make use of high-resolution, high signal-to-noise ratio spectra of four dwarf to turn-off stars, five giant stars, and one sub-giant star observed with THEMIS, HARPS, and UVES to investigate the coherence of the two lines. Results. The two lines provide oxygen abundances that are consistent, within observational errors, in all the giant stars examined by us. On the other hand, for the two dwarf stars for which a measurement was possible, for Procyon, and for the sub-giant star Capella, the 636 nm line provides systematically higher oxygen abundances, as already seen for the Sun. Conclusions. The only two possible reasons for the discrepancy are a serious error in the oscillator strength of the Ni i line blending the 630 nm line or the presence of an unknown blend in the 636 nm line, which makes the feature stronger. The CN lines blending the 636 nm line cannot be responsible for the discrepancy. The Ca i autoionisation line, on the red wing of which the 636 nm line is formed, is not well modelled by our synthetic spectra. However, a better reproduction of this line would result in even higher abundances from the 636 nm, thus increasing the discrepancy.

KW - Line: formation

KW - Radiative transfer

KW - Stars: abundances

KW - Sun: abundances

KW - Sun: photosphere

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