Periodic flare of the 6.7-GHz methanol maser in IRAS 22198+6336

We have detected periodic flares of the 6.7-GHz methanol maser from an intermediate-mass star-forming region IRAS 22198+6336. The maser was monitored daily in 2011, 2012, and 2013. Six flares were observed with a period of 34.6 d. The variation pattern is intermittent, and the flux ratio of the flaring and the quiescent states exceeds 30. Such intermittent variation with the short period uniquely characterizes the variation of the IRAS 22198+6336 maser. At least five spectral components were identified. The spectral components varied almost synchronously, but their peak times differed by 1.8 d. These characteristics can be explained by the colliding-wind binary model.