  Massive B and Be stars produce X-rays from shocks in high velocity winds with
temperatures of a few million degrees and maximum X-ray luminosities of
$\approx$ 10$^{31}$ erg/s. Surprisingly, a sub-group of early Be stars exhibits
> 20 times hotter X-ray temperatures and > 10 times higher X-ray luminosities
than normal. This group of Be stars, dubbed Gamma-Cas analogs, contains about
10 known objects. The origin of this bizarre behavior has been extensively
debated in the past decades. Two mechanisms have been put forward, accretion of
circumstellar disk matter onto an orbiting white dwarf, or magnetic field
interaction between the star and the circumstellar disk (Smith & Robinson
1999). We show here that the X-ray and optical emissions of the prototype of
the class, Gamma-Cas, are very well correlated on year time scales with no
significant time delay. Since the expected migration time from internal disk
regions that emit most of the optical flux to the orbit of the companion star
is of several years, the simultaneity of the high energy and optical fluxes
variations indicates that X-ray emission arises from close to the star. The
systematic lack of magnetic field detection reported in recent
spectro-polarimetric surveys of Be stars is consistent with the absence of
strong magnetic wind braking in these fast spinning stars but put strong
constraints on the possible origin of the magnetic field. We propose that in
Gamma-Cas the magnetic field emerges from equatorially condensed subsurface
convecting layers the thickness of which steeply increases with rotation rate
and that Gamma-Cas and its analogs are the most massive and closest to critical
rotation Be stars
