Precision Analysis of Evolved Stars

TL;DR

This paper reviews the complex late-stage evolution of stars, emphasizing new observational methods like astrometry and interferometry that enhance understanding of stellar mass loss, pulsations, and atmospheres.

Contribution

It highlights the potential of advanced observational techniques to improve modeling and understanding of evolved stars' complex processes.

Findings

Astrometry reveals stellar populations and groupings.

Interferometry enables detailed imaging of stellar atmospheres.

New methods improve insights into stellar mass loss and pulsations.

Abstract

Evolved stars dominate galactic spectra, enrich the galactic medium, expand to change their planetary systems, eject winds of a complex nature, produce spectacular nebulae and illuminate them, and transfer material between binary companions. While doing this, they fill the HR diagram with diagnostic loops that write the story of late stellar evolution. Evolved stars sometimes release unfathomable amounts of energy in neutrinos, light, kinetic flow, and gravitational waves. During these late-life times, stars evolve complexly, with expansion, convection, mixing, pulsation, mass loss. Some processes have virtually no spatial symmetries, and are poorly addressed with low-resolution measurements and analysis. Even a "simple" question as how to model mass loss resists solution. However, new methods offer increasingly diagnostic tools. Astrometry reveals populations and groupings. Pulsations/oscillations support study of stellar interiors. Optical/radio interferometry enable 2-3d imagery of atmospheres and shells. Bright stars with rich molecular spectra and velocity fields are a ripe opportunity for imaging with high spatial and spectral resolution, giving insight into the physics and modeling of later stellar evolution.