  Soft X-ray spectra of ULXs show small deviations from a power-law model, that
can be attributed to reprocessing in a fast, ionized outflow, or to thermal
emission from a cool disk. If it is thermal emission, the cool peak temperature
can be explained by an inner disk that radiates only a small fraction of the
gravitational power, transferring the rest to an upscattering medium which is
then responsible for the dominant power-law component. This scenario does not
require intermediate-mass black holes: we use a phenomenological model to show
that the observed X-ray luminosities and spectra of ULXs are consistent with
typical masses ~ 50-100 Msun.
