Chemistry in AGB stars: successes and challenges

TL;DR

This paper reviews recent advances and ongoing challenges in understanding the molecular chemistry of AGB star envelopes, emphasizing observational, theoretical, and environmental factors affecting chemical processes.

Contribution

It summarizes recent successful modeling approaches for AGB star chemistry and highlights future challenges in the field.

Findings

Advances in modeling inner and outer envelope chemistry

Role of interstellar UV in molecular abundance and distribution

Identification of key challenges for future research

Abstract

Emission and absorption line observations of molecules in late-type stars are a vital component in our understanding of stellar evolution, dust formation and mass loss in these objects. The molecular composition of the gas in the circumstellar envelopes of AGB stars reflects chemical processes in gas whose properties are strong functions of radius with density and temperature varying by more than ten and two orders of magnitude, respectively. In addition, the interstellar UV field plays a critical role in determining not only molecular abundances but also their radial distributions. In this article, I shall briefly review some recent successful approaches to describing chemistry in both the inner and outer envelopes and outline areas of challenge for the future.