Periodic variability of the mainline hydroxyl masers in G9.62+0.20E
  We present the results of a monitoring campaign using the KAT-7 and HartRAO
26m telescopes, of hydroxyl, methanol and water vapour masers associated with
the high-mass star forming region G9.62+0.20E. Periodic flaring of the main
line hydroxyl masers were found, similar to that seen in the 6.7 and 12.2 GHz
methanol masers. The 1667 MHz flares are characterized by a rapid decrease in
flux density which is coincident with the start of the 12.2 GHz methanol maser
flare. The decrease in the OH maser flux density is followed by a slow increase
till a maximum is reached after which the maser decays to its pre-flare level.
A possible interpretation of the rapid decrease in the maser flux density is
presented. Considering the projected separation between the periodic methanol
and OH masers, we conclude that the periodic 12.2 methanol masing region is
located about 1600 AU deeper into the molecular envelope compared to the
location of the periodic OH masers. A single water maser flare was also
detected which seems not to be associated with the same event that gives rise
to the periodic methanol and OH maser flares.
