The solar photospheric abundance of carbon

Abstract

Context. The analysis of the solar spectra using hydrodynamical simulations, with a specific selection of lines, atomic data, and method for computing deviations from local thermodynamical equilibrium, has led to a downward revision of the solar metallicity, Z. We are using the latest simulations computed with the CO5BOLD code to reassess the solar chemical composition. Our previous analyses of the key elements, oxygen and nitrogen, have not confirmed any extreme downward revision of Z, as derived in other works based on hydrodynamical models. Aims. We determine the solar photospheric carbon abundance with a radiation-hydrodynamical CO5BOLD model and compute the departures from local thermodynamical equilibrium by using the Kiel code.Methods. We measured equivalent widths of atomic C i lines on high-resolution, high signal-to-noise ratio solar atlases of disccentre intensity and integrated disc flux. These equivalent widths were analysed with our latest solar 3D hydrodynamical simulation computed with CO5BOLD. Deviations from local thermodynamic equilibrium we computed in 1D with the Kiel code, using the average temperature structure of the hydrodynamical simulation as a background model. Results. Our recommended value for the solar carbon abundance relies on 98 independent measurements of observed lines and is A(C) = 8.50 ± 0.06. The quoted error is the sum of statistical and systematic errors. Combined with our recent results for the solar oxygen and nitrogen abundances, this implies a solar metallicity of Z = 0.0154 and Z/X = 0.0211. Conclusions. Our analysis implies a solar carbon abundance that is about 0.1 dex higher than what was found in previous analyses based on different 3D hydrodynamical computations. The difference is partly driven by our equivalent width measurements (we measure, on average, larger equivalent widths than the other work based on a 3D model), in part because of the different properties of the hydrodynamical simulations and the spectrum synthesis code. The solar metallicity we obtain from the CO5BOLD analyses is in slightly better agreement with the constraints of helioseismology than the previous 3D abundance results.

Solar Models With New Low metal Abundances

“…The heavy-element abundance was revised to Z/ X=0.0181 and Z=0.0134 , hereafter AGS09), Z/X=0.0191 and Z=0.0141 (Lodders et al 2009), and Z/X=0.0211 and Z=0.0154 (Caffau et al 2010). Compared to the SSMs with GS98 mixtures, solar models constructed in accordance to the AGS09 mixtures also disagree with the seismically inferred sound-speed and density profiles, CZ depth, and CZ helium abundance Guzik & Mussack 2010;Serenelli & Basu 2010;Turck-Chièze et al 2010Bi et al 2011;Serenelli et al 2011;Lopes & Turck-Chièze 2013, 2014Le Pennec et al 2015).…”

Sulphur abundances in halo stars from multiplet 3 at 1045 nm

“…A description of these models can be found in . We computed 3D corrections as described in and in Caffau et al (2010).…”

“…In column 9 [S/Fe] is given; both NLTE and ∆ (2) 3D corrections are applied. We adopt A(S)=7.16 for the solar sulphur abundance, as described in Caffau et al (2010). In column 10 the sulphur abundance from Caffau et al (2005) is reported, and in column 11 there is the relative NLTE correction from Takeda et al (2005).…”

Possible Overionization of C II, N II, and O II Ions in the Atmospheres of Early B- and Late O-Type Stars

“…. ± = ε [5] and [8], especially given the very small errors in the determinations of ( ) C logε in Refs. 6, 5, and 8.…”