Abstract
The authors searched for H2O and SiO maser emission in 84 OH/IR stars that have measured IRAS fluxes at 12, 25, and 60 μm. They detected four new H2O sources and eight new SiO sources. The authors have used previous detections reported in the literature to determine the percentage of OH/IR stars with H2O and SiO maser emission as a function of [25-12] color. The percentage of objects with detectable H2O and SiO maser emission decreases with increasing [25-12] color. This color is believed to be an age indicator. The statistical analysis of the data suggests that the percentage of OH/IR stars with SiO maser emission decrease as the [25-12] color increases. Current models for the time evolution of OH/IR stars suggest that it is around [25-12] ≅ +0.2 that the mass loss ceases or decreases significantly. The percentage of OH/IR stars with H2O maser emission decreases significantly at [25-12] ≅ -0.2, before mass loss ceases. The reasons for the early drop in H2O maser percentage are not known.
