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. Prior to the 2015 flaring event there had been no 6.7-GHz methanol maser emission detected toward the MM1 region. The team imaged the MM1 region for all four epochs and the spectrum above confirms that in 2010 there was no associated 6.7-GHz methanol maser emission on milliarcsecond scales with an intensity greater than 1 Jy/beam in the LSR (local standard of rest) velocity range from −12.0 km/s to −4.5 km/s. In contrast, for the October 2015 epoch 6.7-GHz methanol maser emission associated with MM1 is observed over a wide velocity range. 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.