  In order to explain unusually high luminosity and spectral nature of
ultra-luminous X-ray sources (ULXs), some of the underlying black holes are
argued to be of intermediate mass, between several tens to million solar
masses. Indeed, there is a long standing question of missing mass of
intermediate range of black holes. However, as some ULXs are argued to be
neutron stars too, often their unusual high luminosity is argued by
super-Eddington accretions. Nevertheless, all the models are based on
non-magnetized or weakly magnetized accretion. There are, however, evidences
that magnetic fields in accretion discs/flows around a stellar mass black hole
could be million Gauss. Such a magnetically arrested accretion flow plausibly
plays a key role to power many combined disc-jet/outflow systems. Here we show
that flow energetics of a 2.5-dimensional advective magnetized accretion
disc/outflow system around a stellar mass black hole are sufficient to explain
power of ULXs in their hard states. Hence, they are neither expected to have
intermediate mass black holes nor super-Eddington accretors. We suggest that at
least some ULXs are magnetically powered sub-Eddington accretors around a
stellar mass black hole.
