Line formation in solar granulation

VI. [C I], C I, CH and C₂ lines and the photospheric C abundance

¹ Research School of Astronomy and Astrophysics, Mt. Stromlo Observatory, Cotter Rd., Weston, ACT 2611, Australia e-mail: martin@mso.anu.edu.au
² Centre Spatial de Liège, Université de Liège, avenue Pré Aily, 4031 Angleur-Liège, Belgium
³ Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 août, 17, B5C, 4000 Liège, Belgium
⁴ Observatoire Royal de Belgique, avenue circulaire, 3, 1180 Bruxelles, Belgium
⁵ McDonald Observatory and Department of Astronomy, University of Texas, Austin, TX 78712-1083, USA

Received: 6 September 2004
Accepted: 23 October 2004

Abstract

The solar photospheric carbon abundance has been determined from [C i], C i, CH vibration-rotation, CH A-X electronic and C₂ Swan electronic lines by means of a time-dependent, 3D, hydrodynamical model of the solar atmosphere. Departures from LTE have been considered for the C i lines. These turned out to be of increasing importance for stronger lines and are crucial to remove a trend in LTE abundances with the strengths of the lines. Very gratifying agreement is found among all the atomic and molecular abundance diagnostics in spite of their widely different line formation sensitivities. The mean value of the solar carbon abundance based on the four primary abundance indicators ([C i], C i, CH vibration-rotation, C₂ Swan) is , including our best estimate of possible systematic errors. Consistent results also come from the CH electronic lines, which we have relegated to a supporting role due to their sensitivity to the line broadening. The new 3D based solar C abundance is significantly lower than previously estimated in studies using 1D model atmospheres.