Solar and stellar photospheric abundances

Abstract

The determination of photospheric abundances in late-type stars from spectroscopic observations is a well-established field, built on solid theoretical foundations. Improving those foundations to refine the accuracy of the inferred abundances has proven challenging, but progress has been made. In parallel, developments on instrumentation, chiefly regarding multi-object spectroscopy, have been spectacular, and a number of projects are collecting large numbers of observations for stars across the Milky Way and nearby galaxies, promising important advances in our understanding of galaxy formation and evolution. After providing a brief description of the basic physics and input data involved in the analysis of stellar spectra, a review is made of the analysis steps, and the available tools to cope with large observational efforts. The paper closes with a quick overview of relevant ongoing and planned spectroscopic surveys, and highlights of recent research on photospheric abundances.

Solar structure and evolution

“…Lines of helium, an element then not known from the laboratory, were first detected in the solar spectrum; 13 however, these lines are formed under rather uncertain, and very complex, conditions in the upper solar atmosphere, making an accurate abundance determination from the observed line strengths infeasible; the same is true of other noble gases, with neon being a particularly important example. For those elements with lines formed in deeper parts of the atmosphere the spectroscopic analysis yields reasonably precise abundance determinations (e.g., Allende Prieto 2016); however, given that the helium abundance is unknown these are only relative, typically specified as a fraction of the hydrogen abundance. Detailed analyses were provided by Anders and Grevesse (1989) and Grevesse and Noels (1993), the latter leading to a commonly used present ratio Z s =X s ¼ 0:0245 between the surface abundances X s and Z s by mass of hydrogen and elements heavier than helium, respectively.…”

The Laboratory Astrophysics Spectroscopy Programme at Imperial College London

“…There are several review papers concerning laboratory astrophysics which focus on the Fourier spectroscopy technique [1,2], data needed [3,4], the latest results in the field, and projects undertaken by the main groups within it [5,6]. Very detailed and clear descriptions of the need for atomic and molecular data within the field of astronomy can be found in Allende Prieto (2016) [7] and Barklem (2016) [8]. The aim of this paper, rather than to present an exhaustive account of data needs or recent results, is to bring non-experts closer to the field of laboratory astrophysics and the capabilities and practices of our laboratory.…”