OH masers as probes: How does the variability fade away during the AGB - post-AGB transition?

Abstract

We are currently performing a monitoring program of the 1612 MHz OH maser emission of several dozen Galactic disk OH/IR stars with the Nancay Radio Telescope (NRT). They are complemented by several OH/IR stars toward the Galactic center, which were monitored with the Hartebeesthoek radio telescope. We use the maser variations to probe the underlying stellar variability. As early monitoring programs already have shown, some stars are large amplitude variables with periods up to 7 years, others show small or eve…