  We present initial results from a Hubble Space Telescope ultraviolet imaging
survey of stars known to have hot white-dwarf companions which are unresolved
from the ground. The hot companions, discovered through their EUV or UV
emission, are hidden by the overwhelming brightnesses of the primary stars at
visible wavelengths. Out of 17 targets observed, we have resolved eight of them
with the Wide Field Planetary Camera~2, using various ultraviolet filters. Most
of the implied orbital periods for the resolved systems are hundreds to
thousands of years, but in at least three cases (56 Persei, zeta Cygni, and
REJ1925-566) it shouldbe possible to detect the orbital motions within the next
few years, and they may eventually yield new dynamically determined masses for
the white-dwarf components. The 56 Persei and 14 Aurigae systems are found to
be quadruple and quintuple, respectively, including the known optical
components as well as the newly resolved white-dwarf companions. The mild
barium star zeta Cygni, known to have an 18 year spectroscopic period, is
marginally resolved. All of these new resolved Sirius-type binaries will be
useful in determining gravitational redshifts and masses of the white-dwarf
components.
