Morphology and kinematics of the gas envelope of the variable AGB star $\pi^1$ Gruis

TL;DR

This paper analyzes the morphology and kinematics of the gas envelope around the variable AGB star π^1 Gruis using ALMA observations, introducing a new model that better explains the observed data.

Contribution

It presents a new, improved model of the star's circumstellar envelope that accounts for radial winds and smooth velocity transitions from equator to poles.

Findings

The new model fits the ALMA data significantly better than previous models.

The gas envelope shows a complex morphology with radial winds and smooth velocity gradients.

Comparison with earlier SMA data confirms the model's robustness.

Abstract

Observations of the $^{12}$CO(3-2) emission of the circumstellar envelope (CSE) of the variable star $\pi^1$ Gru using the compact array (ACA) of the ALMA observatory have been recently made accessible to the public. An analysis of the morphology and kinematics of the CSE is presented with a result very similar to that obtained earlier for $^{12}$CO(2-1) emission by Chiu et al. (2006) using the Sub-Millimeter Array. A quantitative comparison is made using their flared disk model. A new model is presented that provides a significantly better description of the data, using radial winds and smooth evolutions of the radio emission and wind velocity from the stellar equator to the poles.