The Extraordinary Maser Flaring Event in the Massive Protostellar System NGC6334I: Multi-epoch milliarcsecond resolution investigation of the 6.7-GHz Methanol Masers

Wereportthefirstmulti-epochmilliarcsecondresolutionimagingofthe6.7-GHzclassIImethanolmaseremissionassociated with the high-mass protocluster system NGC6334I. The observations cover 4 epochs over a 10-year period between March 2010 and March 2020. We confirm the emergence of a number of new regions of 6.7-GHz methanol maser emission in the molecular gas surrounding NGC6334-MM1, which lies north of the previously known class II methanol maser sites which are associated with NGC6334-MM3 and -MM2. The new maser emission is located close to the strongest (sub)millimetre source in the NGC6334I cluster MM1B which experienced a sudden increase in intensity in 2015, produced by an episodic accretion event. We are able to compare the location and intensity of the 6.7-GHz methanol maser emission before, during, and after the flare, providing new insights into the relationship between maser flares and periodic accretion events in high-mass stars.