Chemical kinetics models

Spherically symmetric AGB outflows appear to be the exception rather than the rule. Large-scale structures, such as spirals and disks, and small-scale clumpiness is ubiquitously observed. For a chemical model of a circumstellar environment (CSE) to be able to interpret observations, these complexities have to be included.

The Rate22 CSE model is available here, part of the latest release of the UMIST Database for Astrochemistry. The model includes the effects of a close-by stellar companion and a clumpy outflow.

My other models also include a comprehensive dust-gas chemistry, including the formation of ices and refractory organic material on the dust's surface. The disk around L2 Puppis has its own chemical model. While these aren't publicly available yet, I'm happy to chat!

These 1D models can only go so far. Hydrodynamical models are necessary to explain the wide variety of complexities. Coupling chemistry to these models is computationally challenging, but emulating can help! Silke Maes developed the first chemical emulator, MACE, available here. More coming up...

Observations

Chemical models are essential to help interpret the complex dynamics within AGB outflows. For example, chemistry can be used to infer the presence of a stellar companion (like around IRC+10216) and even to infer the orbital parameters (like around W Aql).

Dust-gas chemistry can shed a light on the dust grain-size distribution and can help explain depletion of refractory molecules. There are plenty of chemical tracers for a variety of physics and chemistry, have a look here or feel free to send me an email if you're designing a new observing campaign.

ALMA observations of the disk around L2 Pup are on their way!