From the atmosphere to the circumstellar environment in cool evolved stars

TL;DR

Optical interferometry has significantly advanced our understanding of the atmospheres, molecular shells, dust, and winds of cool evolved stars, informing their evolution and contribution to the interstellar medium.

Contribution

This paper reviews how optical interferometry has enhanced knowledge of the atmospheres and circumstellar environments of cool evolved stars, including RGB, AGB, and RSG stars.

Findings

Improved understanding of stellar atmospheres and molecular shells.

Insights into dust formation and stellar winds.

Implications for stellar evolution and interstellar material return.

Abstract

We discuss and illustrate contributions that optical interferometry has made on our current understanding of cool evolved stars. We include red giant branch (RGB) stars, asymptotic giant branch (AGB) stars, and red supergiants (RSGs). Studies using optical interferometry from visual to mid-infrared wavelengths have greatly increased our knowledge of their atmospheres, extended molecular shells, dust formation, and winds. These processes and the morphology of the circumstellar environment are important for the further evolution of these stars toward planetary nebulae (PNe) and core-collapse supernovae (SNe), and for the return of material to the interstellar medium.