  We have analyzed a ~130 ks XMM-Newton observation of the dynamically
confirmed black hole + Wolf-Rayet (BH+WR) X-ray binary (XB) IC10 X-1, covering
~1 orbital cycle. This system experiences periodic intensity dips every ~35
hours. We find that energy-independent evolution is rejected at a >5 sigma
level. The spectral and timing evolution of IC10 X-1 are best explained by a
compact disk blackbody and an extended Comptonized component, where the thermal
component is completely absorbed and the Comptonized component is partially
covered during the dip. We consider three possibilities for the absorber: cold
material in the outer accretion disk, as is well documented for Galactic
neutron star (NS) XBs at high inclination; a stream of stellar wind that is
enhanced by traveling through the L1 point; and a spherical wind. We estimated
the corona radius (r_ADC) for IC10 X-1 from the dip ingress to be ~1 E+6 km,
assuming absorption from the outer disk, and found it to be consistent with the
relation between r_m ADC and 1--30 keV luminosity observed in Galactic NS XBs
that spans 2 orders of magnitude. For the other two scenarios, the corona would
be larger. Prior BH mass (M_BH) estimates range over 23--38 M_Sun, depending on
the inclination and WR mass. For disk absorption, the inclination, i, is likely
to be ~60--80 degrees, with M_BH ~24--41 M_Sun. Alternatively, the L1-enhanced
wind requires i ~80 degrees, suggesting ~24--33 M_Sun. For a spherical
absorber, i ~ 40 degrees, and M_BH ~50--65 M_Sun.
