Evolved stars with complex atmospheres - the high spectral resolution, mid-IR view

TL;DR

This paper presents high-resolution mid-infrared spectra of red giants' outer atmospheres, revealing their complex structures and introducing new analysis tools to better understand mass-loss mechanisms.

Contribution

It provides observational constraints on red giants' atmospheres using high-resolution spectra and introduces a new non-LTE code for spectral analysis.

Findings

Detection of water vapor lines at 6 microns in red giants

Evidence for complex, non-classical atmospheric structures

Introduction of a new non-LTE analysis tool

Abstract

The physical structures of the outer atmospheres of red giants are not known. They are certainly complex and a range of recent observations are showing that we need to embrace to non-classical atmosphere models to interpret these regions. This region's properties is of importance, not the least, for the understanding of the mass-loss mechanism for these stars, which is not still understood. Here, we present observational constraints of the outer regions of red giants, based on mid-IR, high spectral resolution spectra. We also discuss possible non-LTE effects and highlight a new non-LTE code that will be used to analyse the spectra of these atmospheric layers. We conclude by mentioning our new SOFIA/EXES observations of red giants at 6 microns, where the vibration-rotation lines of water vapour can be detected and spectrally resolved for the first time.