Vol 15, No 5

On the central symmetry of the circumstellar envelope of RS Cnc

Pham Tuyet Nhung, Do Thi Hoai, Jan Martin Winters, Pierre Darriulat, Eric Gérard, Thibaut Le Bertre


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 properties of the CSE. We use a wind model including a bipolar flow with a typical wind velocity of ~8 km s−1 that decreases to ~2 km s−1 near the equator. This wind model is used 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 CSE 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.


Keywords stars: AGB and post-AGB — stars: individual (RS Cnc) — stars: mass loss — radio lines: general

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