Volume 565, May 2014
|Number of page(s)||12|
|Section||Interstellar and circumstellar matter|
|Published online||06 May 2014|
The multi-scale environment of RS Cancri from CO and H I observations⋆
LERMA, UMR 8112, CNRS & Observatoire de Paris, 61 av. de
2 VATLY/INST, 179 Hoang Quoc Viet, Cau Giay, Ha Noi, Vietnam
3 MIT Haystack Observatory, off Route 40, Westford MA 01886, USA
4 IRAM, 300 rue de la Piscine, Domaine Universitairev, 38406 St. Martin d’Hères, France
5 GEPI, UMR 8111, CNRS & Observatoire de Paris, 5 place J. Janssen, 92195 Meudon Cedex, France
Received: 29 January 2014
Accepted: 7 March 2014
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). 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 axisymmetric 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, and also supply additional details 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 ~0.05 pc). The 6′-long H i tail is oriented at a PA of 305°, 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 MHI ≈ 0.0055 M⊙ and estimate a lower limit to the timescale for the formation of the tail to be ~6.4 × 104 years.
Key words: stars: AGB and post-AGB / circumstellar matter / stars: individual: RS Cnc / stars: mass-loss / radio lines: stars / radio lines: ISM
© ESO, 2014
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.