Understanding ULX Nebulae in the Framework of Supercritical Accretion
  For a long time, the well-known supercritically accreting binary SS433 is
being proposed as a prototype for a class of hypothetical bright X-ray sources
that may be identified with the so-called Ultraluminous X-ray sources (ULXs) in
nearby galaxies or at least with part of them. Like SS433, these objects should
be associated with optical nebulae, powered by both radiation of the central
source and its wind or jet activity. Indeed, around many ULXs, bright optical
nebulae (ULX Nebulae, ULXNe) are found. Here, we use SS433 as a prototype for
the power source creating the nebulae around ULXs. Though many factors are
important such as the structure of the host star-forming region and the
possible supernova remnant formed together with the accreting compact object,
we show that most of the properties of ULXNe may be explained by an SS433-like
system evolving for up to about one million years in a constant density
environment. The basic stages of evolution of a ULX Nebula include a
non-spherical HII-region with a central cavity created by non-radiative shock
waves, an elongated or bipolar shock-powered nebula created by jet activity and
a large-scale quasi-spherical bubble.
