Kashima 34-m Water Maser Survey of Late-Type Stars

This paper presents new results of a water maser survey of late-type stellar objects at 22.235GHz with the Kashima 34-m radio telescope. We have detected 179 out of 643 observed sources, including 32 new detections. The sources were selected in terms of the IRAS flux density and colors of late-type stars, involving optically observable Mira/semiregular variables, IRC objects, OH/IR sources and protoplanetary nebulae. We found the highest H₂O detection rate for the type of stars with a thin dust envelope (Mira/semiregular variables) among other types of sources. This is attributed to the smaller distances to such stars in the sample. The velocity spread of the H₂O maser profile has an increasing tendency with the IRAS color, though it becomes more difficult to access this color dependence beyond an edge of the transition of the (oxygen-rich) Asymptotic Giant Branch stars to protoplanetary nebulae in the two-color diagram.