Formation of Mn I lines in the solar atmosphere ^*,**

Institute for Astronomy and Astrophysics, Ludwig-Maximilian University, Scheinerstr. 1, 81679 Munich, Germany e-mail: mbergema@usm.lmu.de

Received: 24 November 2006
Accepted: 3 July 2007

Abstract

Context.We present a detailed NLTE analysis of 39 lines in the solar spectrum. The influence of NLTE effects on the line formation and element abundance is investigated.

Aims.Our goal is the derivation of solar values for manganese lines, which will later be used in differential abundance analyses of metal-poor stars.

Methods.The method of spectrum synthesis is employed, which is based on a solar model atmosphere with initially specified element abundances. A manganese abundance of dex is used with the theoretical line-blanketed model atmosphere. Statistical equilibrium calculations are carried out for the model atom, which comprises 245 and 213 levels for and , respectively. Photoionization cross-sections are assumed hydrogenic.

Results.For line synthesis van der Waals broadening is calculated according to Anstee & O'Mara's formalism. It is shown that hyperfine structure of the Mn lines also has strong broadening effects, and that manganese is prone to NLTE effects in the solar atmosphere. The nature of the NLTE effects and the validity of the LTE approach are discussed in detail. The role of photoionization and collisional interaction is investigated.

Conclusions.Maximum NLTE corrections of +0.1 dex with respect to LTE profiles are found. We propose an absolute solar abundance of 5.36 dex. The main source of errors in the abundance calculations is uncertain oscillator strengths.