2004ApJ...610L..41N

We report results of an interferometric observation toward an SiO maser source, IRAS 19312+1950, in the HCO⁺ J=1-0 line with the Berkeley-Illinois-Maryland Association millimeter array. In the spatially integrated spectrum of HCO⁺, two kinematic components were seen: a strong line with a narrow width (∼2km/s, narrow component) and a weak symmetric line with a broad width (∼60km/s, broad component). The line profile of HCO⁺ is reminiscent of that of CO. In the integrated intensity map, we found a pronounced bipolar shape consisting of the lower velocity part of the broad component. The higher velocity part of the broad component originated in a relatively small region (≲3"). The spatial structure of the narrow component clearly correlates with near-infrared structure. The position-velocity diagrams indicate the presence of a bipolar outflow with an expansion velocity of about 10 km/s. On the basis of the present results, we suggest that the nature of the bipolar flow seen in IRAS 19312+1950 is explained by the hydrodynamical interaction between an asymptotic giant branch wind and ambient material with axial symmetric structure.