  Supercritical accretion onto compact objects powers a massive wind that is
optically thick and Eddington-limited. If most of the hard X-rays from the
central disk are obscured by the wind, the source will display a blackbody-like
spectrum with a luminosity scaled with the mass of the compact object. From the
Chandra archive of nearby galaxies, we selected a sample of luminous and very
soft sources and excluded contaminations from foreground objects and supernova
remnants. They are found to be preferentially associated with late-type
galaxies. The majority of sources in our sample are either too hot or too
luminous to be explained by nuclear burning on the surface of white dwarfs, and
are argued to be powered by accretion. The most likely explanation is that they
are due to emission from the photosphere of a wind driven by supercritical
accretion onto compact objects. Their blackbody luminosity ranges from ~10^37
to nearly 10^40 erg/s, indicative of the presence of both neutron stars and
stellar-mass black holes. The blackbody luminosity also shows a possible
bimodal distribution, albeit at low significance, peaked around the Eddington
limit for neutron stars and stellar-mass black holes, respectively. If this can
be confirmed, it will be smoking gun evidence that supercritical accretion
powers thick winds. Based on a wind model, the inferred mass accretion rate of
these objects is around a few hundred times the Eddington rate, suggesting that
they may be intermediate between the canonical ultraluminous X-ray sources and
SS 433 in terms of the accretion rate.
