A Reappraisal of the Solar Photospheric C/O Ratio

An accurate determination of photospheric solar abundances requires detailed modeling of the solar granulation and accounting for departures from local thermodynamical equilibrium (LTE). We argue that the forbidden C I line at 8727 Å is largely immune to departures from LTE and can be realistically modeled using LTE radiative transfer in a time-dependent three-dimensional simulation of solar surface convection. We analyze the [C I] line in the solar flux spectrum to derive the abundance log ϵ(C) = 8.39 ± 0.04 dex. Combining this result with our parallel analysis of [O I] λ6300, we find C/O = 0.50 ± 0.07, in agreement with the ratios measured in the solar corona from gamma-ray spectroscopy and solar energetic particles.

[1]  P. MacQueen,et al.  Convective Wavelength Shifts in the Spectra of Late-Type Stars , 2002, astro-ph/0201355.

[2]  R. Wimmer–Schweingruber.  Joint SOHO/ACE workshop "Solar and Galactic Composition" , 2001 .

[3]  S. Wedemeyer.  Statistical equilibrium and photospheric abundance of silicon in the Sun and in Vega , 2001 .

[4]  M. Asplund,et al.  Chemical Abundances from Inversions of Stellar Spectra: Analysis of Solar-Type Stars with Homogeneous and Static Model Atmospheres , 2001, astro-ph/0105262.

[5]  M. Asplund,et al.  On OH line formation and oxygen abundances in metal-poor stars , 2001, astro-ph/0104071.

[6]  J. Schmelz,et al.  The Solar Maximum Mission , 1999 .

[7]  Bernhard Haisch,et al.  The Many Faces of the Sun : A Summary of the Results from NASA's Solar Maximum Mission , 1999 .

[8]  C. Esteban,et al.  Chemical composition of the Orion nebula derived from echelle spectrophotometry , 1998 .

[9]  C. Prieto,et al.  Fe i line shifts in the optical spectrum of the Sun , 1997, astro-ph/9710066.

[10]  J. Grove,et al.  Accelerated Particle Composition and Energetics and Ambient Abundances from Gamma-Ray Spectroscopy of the 1991 June 4 Solar Flare , 1997 .

[11]  C. Mendoza,et al.  Atomic data from the IRON Project - XXII. Radiative rates for forbidden transitions within the ground configuration of ions in the carbon and oxygen isoelectronic sequences , 1997 .

[12]  A. Witt,et al.  Interstellar Depletions Updated: Where All the Atoms Went , 1996 .

[13]  D. Reames.  Coronal abundances determined from energetic particles , 1995 .

[14]  S. Johansson,et al.  A New Multiplet Table for Fe , 1994, astro-ph/9404049.

[15]  É. Biémont,et al.  New f-values in C I and the CNO abundances in the sun , 1993 .

[16]  S. Adelman,et al.  ELEMENTAL ABUNDANCES OF THE B6 IV STAR XI OCTANTIS , 1993 .

[17]  Robert L. Kurucz,et al.  SYNTHE Spectrum Synthesis Programs and Line Data. , 1993 .

[18]  Douglas R. Gies,et al.  Carbon, Nitrogen, and Oxygen Abundances in Early B-Type Stars , 1992 .

[19]  William H. Press,et al.  Numerical recipes , 1990 .

[20]  J. R. Letaw,et al.  Nuclear line spectroscopy of the 1981 april 27 solar flare , 1990 .

[21]  Ingemar Furenlid,et al.  Solar flux atlas from 296 to 1300 nm , 1985 .

[22]  J. Swings,et al.  Forbidden nitrogen I lines in the infra-red solar spectrum , 1967 .

[23]  J. Swings,et al.  Forbidden carbon I lines in the solar spectrum , 1967 .

[24]  J. Ward,et al.  Measurement and Calculation of Cu II, Ge II, Si II, and C I Vacuum-Ultraviolet Lines , 1966 .

[25]  John A. Nelder,et al.  A Simplex Method for Function Minimization , 1965, Comput. J..

[26]  Space Science Reviews , 1962, Nature.

[27]  A. Unsöld,et al.  Physik der Sternatmosphären , 1938 .

[28]  K. Schwarzschild,et al.  The Observatory , 1886 .