  Accretion onto protostars may occur in sharp bursts. Accretion bursts during
the embedded phase of young protostars are probably most intense, but can only
be inferred indirectly through long-wavelength observations. We perform
radiative transfer calculations for young stellar objects (YSOs) formed in
hydrodynamic simulations to predict the long wavelength, sub-mm and mm, flux
responses to episodic accretion events, taking into account heating from the
young protostar and from the interstellar radiation field. We find that the
flux increase due to episodic accretion events is more prominent at sub-mm
wavelengths than at mm wavelengths; e.g. a factor of ~570 increase in the
luminosity of the young protostar leads to a flux increase of a factor of 47 at
250 micron but only a factor of 10 at 1.3 mm. Heating from the interstellar
radiation field may reduce further the flux increase observed at longer
wavelengths. We find that during FU Ori-type outbursts the bolometric
temperature and luminosity may incorrectly classify a source as a more evolved
YSO, due to a larger fraction of the radiation of the object being emitted at
shorter wavelengths
