Comparative Modelling of the Spectra of Cool Giants

TL;DR

This study compares different stellar atmosphere models and analysis strategies for high-resolution spectra of cool giant stars, highlighting the variability in derived parameters and the influence of physical inputs and methods.

Contribution

It provides a comprehensive comparison of various spectral synthesis codes and analysis approaches, revealing the sources of discrepancies in stellar parameter determination.

Findings

Different analysis methods yield a wide range of stellar parameters.

Discrepancies mainly arise from physical input data and analysis details.

Current models and methods are not yet definitive for abundance analysis.

Abstract

Our ability to extract information from the spectra of stars depends on reliable models of stellar atmospheres and appropriate techniques for spectral synthesis. Various model codes and strategies for the analysis of stellar spectra are available today. We aim to compare the results of deriving stellar parameters using different atmosphere models and different analysis strategies. The focus is set on high-resolution spectroscopy of cool giant stars. Spectra representing four cool giant stars were made available to various groups and individuals working in the area of spectral synthesis, asking them to derive stellar parameters from the data provided. The results were discussed at a workshop in Vienna in 2010. Most of the major codes currently used in the astronomical community for analyses of stellar spectra were included in this experiment. We present the results from the different groups, as well as an additional experiment comparing the synthetic spectra produced by various codes for a given set of stellar parameters. Similarities and differences of the results are discussed. Several valid approaches to analyze a given spectrum of a star result in quite a wide range of solutions. The main causes for the differences in parameters derived by different groups seem to lie in the physical input data and in the details of the analysis method. This clearly shows how far from a definitive abundance analysis we still are.