2000A&A...353..257B

We report on high-resolution CO J=1-0 and J=2-1 interferometric observations of the oxygen-rich semiregular variable RV Boo supplemented by single-dish multi-transition data of CO(J=1-0, 2-1, 3-2, 4-3). Detections of the thermal SiO(v=0, J=2-1, 3-2) transitions as well as the vibrationally excited SiO(v=1, J=2-1) line are also reported. The interferometric CO J=2-1 observations, with a spatial resolution of about 1.7", reveal a disk-like structure of size 4.2"x3.3" around RV Boo. Furthermore, the position-velocity information along a line through the center of the source at a position angle of about 150° can be interpreted as a sign of Keplerian rotation. Six symmetrically placed features, possibly corresponding to three rings, around a central feature are seen. These observations may therefore, to our knowledge, present the first indications of a rotating disk around an AGB star. However, it cannot be fully excluded that the observed kinematical structure is caused by a bipolar outflow. From the single-dish CO observations we estimate the molecular mass of the source to be 3x10^–5M_☉.