Due to high brightness and low interstellar extinction at 6.7 GHz, class II methanol masers are useful for studying the physical properties of massive young stellar objects. Since they usually originate within 1000 AU from the protostar and are pumped by IR photons, their variability can be a fairly good marker of protostellar activity. Our monitoring of the 6.7 GHz methanol masers in Cep A revealed quasi-periodic low-amplitude red-shifted flares. Thus we decided to examine this phenomenon in EVN projects RD002 and ED046B.
Cepheus A is a well-known, well-studied high-mass star-forming region located only 700pc away, which hosts a cluster of young stellar objects. The brightest continuum source, HW2, is an HMYSO with a mass of $\sim$10M$_{\odot}$ and bolometric luminosity of 2$\times$10 $^{\mathrm{4}}$L$_{\odot}$.
Our results, combined with previous VLBI observations, pinpoint flaring cloudlets near the presumed edge of a dust emission core.