SUBMILLIMETER WATER MASERS IN CIRCUMSTELLAR ENVELOPES .2. VARIABILITY

Near-simultaneous observations of circumstellar 22-, 321- and 325-GHz water masers have been made at four epochs between 1992 March 1 and 19 93 April 17. All nine sources studied have varied significantly, typic ally by factors of 2 or more, in all lines, and there have been major changes of profile shape in many cases. The 321-GHz line is generally the most variable, having the largest amplitudes of variation and shor test time-scales. Time-scales to vary by a factor of 2 were as short a s 3 weeks. The variations in the 22-, 321- and 325-GHz masers are not particularly well correlated: in some cases they are completely antico rrelated. The variability data are presented in detail, and their impl ications for the H2O maser excitation are briefly discussed.