Accretion bursts in high-mass protostars

Recent observations of high-mass young stellar objects (HMYSOs) with masses M∗≥10 M⊙ uncovered outbursts with accretion rates exceeding ～10‑3 M⊙ yr‑1. We utilise 1D time-dependent models of protoplanetary discs around HMYSOs to study burst properties. We find that discs around HMYSOs are much hotter than those around their low-mass cousins. As a result, a much more extended region of the disc is prone to the thermal hydrogen ionisation and magnetorotational (MRI) activation instabilities. The outbursts triggered by these instabilities, however, always have too low accretion rates and are one to several orders of magnitude too long compared to those observed from HMYSOs to date. On the other hand, bursts generated by tidal disruptions of gaseous giant planets formed by the gravitational instability of the protoplanetary discs yield properties commensurate with observations, provided that the clumps are in the post-collapse configuration with planet radius Rp≥10 Jupiter radii.