Study of variable stars associated with maser sources: G025.65+1.05
  We report variation of K-band infrared (IR) emission in the vicinity of the
G025.65+1.05 water and methanol maser source. New observational data were
obtained with 2.5m telescope of the Caucasian Mountain Observatory (CMO) of
Moscow State University on 2017-09-21 during the strong water maser flare. We
found that the IR source situated close to the maser position had decreased
brightness in comparison to archive data. This source is associated with a
massive young stellar object (MYSO) corresponding to the compact infrared
source IRAS 18316-0602 (RAFGL 7009S). Similar decrease in K-brightness of the
IR source close to the maser position was observed in March~2011 when the water
maser activity was increased. The dips in MYSO brightness can be related to the
maser flare phases. Maser flares that are concurrent with dips of the IR
emission can be explained if the lower IR radiation field enables more
efficient sink of the pumping cycle by allowing IR photons to escape the maser
region.
