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We report the discovery of 6.7 GHz methanol maser periodic flares in fourmassive star forming regions and the updated light curve for the known periodicsource G22.357+0.066. The observations were carried out with the Torun 32 mradio telescope between June 2009 and April 2014. Flux density variations withperiod of 120 to 245 d were detected for some or all spectral features. Avariability pattern with a fast rise and relatively slow fall on time-scale of30-60 d dominated. A reverse pattern was observed for some features ofG22.357+0.066, while sinusoidal-like variations were detected in G25.411+0.105.A weak burst lasting ~520 d with the velocity drift of 0.24 km/s/yr occurred inG22.357+0.066. For three sources for which high resolution maps are available,we found that the features with periodic behaviour are separated by more than500 au from those without any periodicity. This suggests that the maser flaresare not triggered by large-scale homogeneous variations in either thebackground seed photon flux or the luminosity of the exciting source and amechanism which is able to produce local changes in the pumping conditions isrequired.

Discovery of four periodic methanol masers and updated light curve for a further one