On the central symmetry of the circumstellar envelope of RS Cnc

TL;DR

This study analyzes CO emission from RS Cnc's circumstellar envelope, revealing significant asymmetries and wind structure details, advancing understanding of AGB star mass-loss processes.

Contribution

It introduces a wind model with bipolar flow and quantifies asymmetries in RS Cnc's envelope using combined interferometric and single dish data.

Findings

Detection of north-south asymmetries in the envelope

Wind velocity decreases from 8 km/s to 2 km/s near the equator

Parameters for wind morphology and temperature distribution obtained

Abstract

We present a phenomenological study of CO(1-0) and CO(2-1) emission from the circumstellar envelope (CSE) of the Asymptotic Giant Branch (AGB) star RS\,Cnc. It reveals departures from central symmetry that turn out to be efficient tools for the exploration of some of the CSE properties. We use a wind model including a bipolar flow with a typical wind velocity of $\sim$8 km\,s$^{-1}$ decreasing to $\sim$2 km\,s$^{-1}$ near the equator to describe Doppler velocity spectral maps obtained by merging data collected at the IRAM Plateau de Bure Interferometer and Pico Veleta single dish radio telescope. Parameters describing the wind morphology and kinematics are obtained, together with the radial dependence of the gas temperature in the domain of the circumstellar envelope probed by the CO observations. Significant north-south central asymmetries are revealed by the analysis, which we quantify using a simple phenomenological description. The origin of such asymmetries is unclear.