Chemistry in AGB stars: successes and challenges

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.

To appear in the refereed proceedings of the 11th Pacific Rim Conference on Stellar Astrophysics held in Hong Kong, Dec.14-17, 2015, Sun Kwok (editor). 10 pages, 2 figures

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• First detection of methanol towards a post-AGB object, HD101584
• How to disentangle geometry and mass-loss rate from AGB-star spectral energy distributions -- The case of EP Aqr
• Asymmetries in asymptotic giant branch stars and their winds. I. From 3D RHD models to synthetic observables