  We present a study of the early (days to weeks) X-ray and UV properties of
eight Type Ia supernovae (SNe Ia) which have been extensively observed with the
X-Ray Telescope (XRT) and UV/Optical Telescope (UVOT) onboard Swift, ranging
from 5-132 days after the outburst. SN 2005ke is tentatively detected (at a
3-3.6 sigma level of significance) in X-rays based on deep monitoring with the
XRT ranging from 8 to 120 days after the outburst. The inferred X-ray
luminosity [(2+/-1) x 10^{38} ergs/s; 0.3-2 keV band] is likely caused by
interaction of the SN shock with circumstellar material (CSM), deposited by a
stellar wind from the progenitor's companion star with a mass-loss rate of ~ 3
x 10^{-6} M_sun/yr (v_w/10 km/s). Evidence of CSM interaction in X-rays is
independently confirmed by an excess of UV emission as observed with the UVOT
onboard Swift, starting around 35 days after the explosion. The non-detection
of SN 2005ke with Chandra 105 days after the outburst implies a rate of decline
steeper than L_x \propto t^{-0.75}, consistent with the decline expected from
the interaction of the SN shock with a spherically symmetric CSM (t^{-1}). None
of the other seven SNe Ia is detected in X-rays or shows a UV excess, which
allows us to put tight constraints on the mass-loss rates of the progenitor
systems.
