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 \sim 1 ^ { \prime \prime } ( \sim 150 AU ) to \sim 6 ^ { \prime } ( \sim 0.25 pc ) .
Our study utilizes new CO1-0 data from the Plateau-de-Bure Interferometer and new H i 21-cm line observations from the Jansky Very Large Array ( JVLA ) , in combination with previous observations .
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 JVLA H i 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 H i 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 \sim 0.05 pc ) .
The 6 ^ { \prime } -long H i ‘ tail ’ is oriented at a PA of 305 ^ { \circ } , consistent with the space motion of the star .
The tail is resolved into several clumps that may result from hydrodynamic effects linked to the interaction with the local interstellar medium .
We measure a total mass of atomic hydrogen M _ { HI } \approx 0.0055 M _ { \odot } and estimate a lower limit to the timescale for the formation of the tail to be \sim 6.4 \times 10 ^ { 4 } years .