The multi-scale environment of RS Cnc from CO and HI observations

Abstract

We present a detailed study of the circumstellar gas distribution and kinematics of the semi-regular variable star RS Cnc on spatial scales ranging from ~1" (~150 AU) to ~6' (~0.25 pc). New modeling of CO1-0 and CO2-1 imaging observations leads to a revised characterization of RS Cnc's previously identified axisymmetric molecular outflow. Rather than a simple disk-outflow picture, we find that a gradient in velocity as a function of latitude is needed to fit the spatially resolved spectra, and in our preferred model, the density and the velocity vary smoothly from the equatorial plane to the polar axis. In terms of density, the source appears quasi-spherical, whereas in terms of velocity the source is axi-symmetric with a low expansion velocity in the equatorial plane and faster outflows in the polar directions. The flux of matter is also larger in the polar directions than in the equatorial plane. An implication of our model is that the stellar wind is still accelerated at radii larger than a few hundred AU, well beyond the radius where the terminal velocity is thought to be reached in an asymptotic giant branch star. The HI data show the previously detected head-tail morphology, but also supply additional detail about the atomic gas distribution and kinematics. We confirm that the `head' seen in HI is elongated in a direction consistent with the polar axis of the molecular outflow, suggesting that we are tracing an extension of the molecular outflow well beyond the molecular dissociation radius (up to ~0.05 pc). The 6'-long HI `tail' is oriented at a PA of 305°, consistent with the space motion of the star. We measure a total mass of atomic hydrogen ~0.0055 solar mass and estimate a lower limit to the timescale for the formation of the tail to be ~6.4x10^4 years. (abridged)

arXiv commentaccepted for publication in Astronomy & Astrophysics

References in corpus (26)

• Local Kinematics and the Local Standard of Rest
• Fast core rotation in red-giant stars revealed by gravity-dominated mixed modes
• The Expanded Very Large Array -- a New Telescope for New Science
• Local kinematics of K and M giants from Coravel/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters
• Evolution, nucleosynthesis and yields of low mass AGB stars at different metallicities (II): the FRUITY database
• Models of circumstellar molecular radio line emission: Mass loss rates for a sample of bright carbon stars
• Preplanetary Nebulae: An HST Imaging Survey and a New Morphological Classification System
• Multiple Molecular Winds in Evolved Stars I. A Survey of CO(2-1) and CO(3-2) Emission from 45 Nearby AGB Stars
• On the reliability of mass-loss-rate estimates for AGB stars
• News on the s process from young open clusters
• Disk Formation by AGB Winds in Dipole Magnetic Fields
• The dynamical evolution of the circumstellar gas around low-and intermediate-mass stars I: the AGB
• HI in circumstellar environments
• Ram pressure stripping in Planetary Nebulae
• Vortices in the wakes of AGB stars
• Discovery of an HI Counterpart to the Extended Tail of Mira
• The Interaction of Asymptotic Giant Branch Stars with the Interstellar Medium
• The formation of a detached shell around the carbon star Y CVn
• VLA Observations of HI in the Circumstellar Envelopes of Asymptotic Giant Branch Stars
• HI and CO in the circumstellar environment of the S-type star RS Cnc
• HI Observations of the Asymptotic Giant Branch Star X Herculis: Discovery of an Extended Circumstellar Wake Superposed on a Compact High-Velocity Cloud
• ALMA Observations of the Coldest Place in the Universe: The Boomerang Nebula
• Disk-Like Structure in the Semi-Regular Pulsating Star, X Her
• Atomic hydrogen in AGB circumstellar environments. A case study: X Her
• An HI Imaging Survey of Asymptotic Giant Branch Stars
• A latitude-dependent wind model for Mira's cometary head

Cited by in corpus (10)

• The morpho-kinematics of the circumstellar envelope around the AGB star EP Aqr
• Observation of narrow polar jets in the nascent wind of oxygen-rich AGB star EP Aqr
• 12CO emission from EP Aqr: Another example of an axi-symmetric AGB wind?
• Space reconstruction of the morphology and kinematics of axisymmetric radio sources
• ALMA observations of the circumstellar envelope around EP Aqr
• Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri
• HI line observations of 290 evolved stars made with the Nancay Radio Telescope -- I. Data
• De-projection of radio observations of axi-symmetric expanding circumstellar envelopes
• On the central symmetry of the circumstellar envelope of RS Cnc
• Morphology and kinematics of the gas envelope of the variable AGB star ${\pi }^1$ Gruis