Burst occurrence in young massive stellar objects
  Episodic accretion-driven outbursts are an extreme manifestation of accretion
variability. It has been proposed that the development of gravitational
instabilities in the proto-circumstellar medium of massive young stellar
objects (MYSOs) can lead to such luminous bursts, when clumps of fragmented
accretion discs migrate onto the star. We simulate the early evolution of MYSOs
formed by the gravitational collapse of rotating 100 M pre-stellar cores and
analyze the characteristics of the bursts that episodically accompany their
strongly time-variable protostellar lightcurve. We predict that MYSOs spend ~
10^3 yr (~ 1.7\%) of their modelled early 60 kyr experiencing eruptive phases,
during which the peak luminosity exceeds the quiescent pre-burst values by
factors from 2.5 to more than 40. Throughout these short time periods, they can
acquire a substential fraction (up to ~ 50 \%) of their zero-age-main sequence
mass. Our findings show that fainter bursts are more common than brighter ones.
We discuss our results in the context of the known bursting MYSOs, e.g.
NGC6334I-MM1 and S255IR-NIRS3, and propose that these monitored bursts are part
of a long-time ongoing series of eruptions, which might, in the future, be
followed by other luminous flares.
