Kumar et al. report the first multi-epoch milliarcsecond resolution imaging of 6.7-GHz methanol maser emission associated with the high-mass protocluster system NGC 6334I. The observations, made with the southern hemisphere Long Baseline Array (LBA), cover four epochs March 2010 and March 2020. LBA observations were made in March 2010, July 2010, October 2015 and March 202, with the ATCA, Parkes, Mopra, Ceduna, Hobart, Katherine, Hartebeesthoek (South Africa) and Warkworth (New Zealand) telescopes all participating in at least one epoch. The 6.7-GHz methanol maser emission from NGC6334I has been regularly monitored with the Hartebeesthoek radio telescope since 1999 (MacLeod et al. 2018). A flare was detected in multiple maser species (methanol, OH, and water) commencing in January 2015 and peaking in August 2015.

The figure above shows the 6.7-GHz methanol maser distribution in NGC6334I across all four epochs and shows how it has changed.  In particular, it highlights the significant changes in the maser clusters to the south and south-west of MM1 between 2015 and 2020 and the change in the extent of the MM2 and MM3 emissions over the 10-year period. Comparison of the location and intensity of the 6.7-GHz methanol maser emission before, during, and after the flare, provides new insights into the relationship between maser flares and episodic accretion events in high-mass stars.