  We report the XMM-Newton observation of a large X-ray flare from the Herbig
Ae star V892 Tau. The apparent low mass companion of V892 Tau, V892 Tau NE, is
unresolved by XMM-Newton. Nevertheless there is compelling evidence from
combined XMM-Newton and Chandra data that the origin of the flare is the Herbig
Ae star V892 Tau. During the flare the X-ray luminosity of V892 Tau increases
by a factor of ~15, while the temperature of the plasma increases from kT ~ 1.5
keV to kT ~ 8 keV. From the scaling of the flare event, based on hydrodynamic
modeling, we conclude that a 500 G magnetic field is needed in order to confine
the plasma. Under the assumptions that a dynamo mechanism is required to
generate such a confining magnetic field and that surface convection is a
necessary ingredient for a dynamo, our findings provide indirect evidence for
the existence of a significant convection zone in the stellar envelope of
Herbig Ae stars.
