Line formation in convective stellar atmospheres. I. Granulation corrections for solar photospheric abundances

TL;DR

This paper investigates how temperature fluctuations in the Sun's photosphere affect spectroscopic abundance measurements by comparing 1D and 2D models, providing correction tables to improve accuracy.

Contribution

It introduces 'granulation abundance corrections' derived from 2D simulations to adjust 1D spectroscopic abundance determinations for photospheric inhomogeneities.

Findings

Temperature inhomogeneities generally strengthen spectral lines.

Abundance corrections can be estimated from provided tables and graphs.

Corrections help identify lines least affected by temperature fluctuations.

Abstract

In an effort to estimate the largely unknown effects of photospheric temperature fluctuations on spectroscopic abundance determinations, we have studied the problem of LTE line formation in the inhomogeneous solar photosphere based on detailed 2-dimensional radiation hydrodynamics simulations of the convective surface layers of the Sun. By means of a strictly differential 1D/2D comparison of the emergent equivalent widths, we have derived "granulation abundance corrections" for individual lines, which have to be applied to standard abundance determinations based on homogeneous 1D model atmospheres in order to correct for the influence of the photospheric temperature fluctuations. In general, we find a line strengthening in the presence of temperature inhomogeneities as a consequence of the non-linear temperature dependence of the line opacity. For many lines of practical relevance, the magnitude of the abundance correction may be estimated from interpolation in the tables and graphs provided with this paper. The application of abundance corrections may often be an acceptable alternative to a detailed fitting of individual line profiles based on hydrodynamical simulations. The present study should be helpful in providing upper bounds for possible errors of spectroscopic abundance analyses, and for identifying spectral lines which are least sensitive to the influence of photospheric temperature inhomogeneities.