H2o Maser Observations of Candidate Post-agb Stars and Discovery of Three High-velocity Water Sources

We present the results of 22 GHz H2O maser observations of a sample of 85 post-Asymptotic Giant Branch (post-AGB) candidate stars, selected on the basis of their OH 1612 MHz maser and far-infrared properties. All sources were observed with the Tidbinbilla 70-m radio telescope and 21 detections were made. 86 GHz SiO Mopra observations of a subset of the sample are also presented. Of the 21 H2O detections, 15 are from sources that are likely to be massive AGB stars and most of these show typical, regular H2O maser profiles. In contrast, nearly all the detections of more evolved stars exhibited high-velocity H2O maser emission. Of the five sources seen, v223 (W43A, IRAS 18450−0148) is a well known ‘water-fountain’ source which belongs to a small group of post-AGB stars with highly collimated, high-velocity H2O maser emission. A second source in our Affiliated with the CSIRO Australia Telescope National Facility