SIMBAD references

The history of mass loss during the AGB phase is key to understanding the stellar evolution and the gas and dust replenishment of the interstellar medium. The mass-loss phenomenon presents fluctuations with a wide variety of timescales and spatial scales and requires combining data from multiple tracers. We study the respective contributions of the central source and of the external medium to the complex geometry of circumstellar ejecta. This paper presents Plateau de Bure Interferometer and IRAM 30-m telescope CO rotational line observations, along with HI data obtained with the Nancay Radio Telescope for the oxygen-rich semi-regular variable RSCnc, in order to probe its circumstellar environment on different scales. We detect both the CO(1-0) and the CO(2-1) rotational lines from RSCnc. The line profiles are composite, comprising two components of half-width ∼2km/s and ∼8km/s, respectively. Whereas the narrow velocity component seems to originate in an equatorial disk in the central part of the CO envelope, the broad component reveals a bipolar structure, with a north-south velocity gradient. In addition, we obtain new HI data on the source and around it in a field of almost 1 square degree. The HI line is centered on v_LSR=7km/s in agreement with CO observations. A new reduction process reveals a complex extended structure in the northwest direction, of estimated size ∼18', with a position angle (∼310°) opposite the direction of the stellar proper motion (∼140°). We derive an HI mass of ∼3x10^–2M_☉ for this structure. Based on a non spherical simulation, we find that this structure is consistent with arising from the interaction of the star undergoing mass loss at an average rate of ∼10^–7M_☉/yr over ∼2-3x10⁵ years with the interstellar medium. Using CO and HI lines, we show that the circumstellar environment around RS Cnc includes two related but well separated regions. With CO, we find a bipolar geometry that probably originates from the intrinsic behavior of recent mass-loss processes. With Hi, we find a trail of gas, in a direction opposite to the proper motion of RSCnclending support to the hypothesis of an interaction with the interstellar medium. This work illustrates the powerful complementarity of CO and Hiobservations with regard to a more complete description of circumstellar environments around AGB stars.