Time variations of interstellar water masers in HII regions

Abstract

Fourteen water maser sources associated with HII regions have been monitored over the period September 1974-May 1977. Time variations have been observed with a range of time-scales from days to years. A statistical analysis of the short- and long-term variations is performed and related variability in features of similar velocity is examined. The time variations must be due to changes in the pump input, geometry or other physical properties of the maser regions but at present no adequate theory exists to describe the complex behavior observed