# The Role of Internal Photons on the Chemistry of the Circumstellar Envelopes of AGB Stars

## TL;DR

This paper investigates how internal stellar photons influence the chemical composition of AGB star circumstellar envelopes, revealing significant effects within a few stellar radii and implications for dust formation and binary interactions.

## Contribution

It extends existing models to include stellar blackbody photons, demonstrating their impact on CSE chemistry in clumpy, porous environments around AGB stars.

## Key findings

- Internal photons can alter chemistry within a few stellar radii.
- Photon influence extends to several hundred stellar radii for some molecules.
- Harder radiation from companions significantly affects inner CSE chemistry.

## Abstract

Recent high spatial resolution observations of gas and dust in the circumstellar envelopes (CSEs) of AGB stars indicate morphologies much more complex than the smooth density distributions generated by spherically symmetric, constant mass loss rates. In particular, the observation of spiral arcs and disks indicate the likely presence of a binary companion which in some cases give rise to the UV photons detected by GALEX. In this Article, we extend our recent model of the chemistry in a clumpy, porous CSE around an AGB star to include the influence of stellar blackbody photons on the CSE chemistry. Our results indicate that internal photons, in a clumpy, porous CSE, can alter chemistry within a few stellar radii and, for some molecules, alter abundances out to several hundred stellar radii. They further suggest that harder radiation from companion stars or accretion disks will have a substantial impact on chemistry in the dust formation zones and inner CSEs of AGB stars.