  We present an analysis of X-ray and ultra-violet data of the dwarf nova VW
Hyi that were obtained with XMM-Newton during the quiescent state. The X-ray
spectrum indicates the presence of an optically thin plasma in the boundary
layer that cools as it settles onto the white dwarf. The plasma has a
continuous temperature distribution that is well described by a power-law or a
cooling flow model with a maximum temperature of 6-8 keV. We estimate from the
X-ray spectrum a boundary layer luminosity of 8*10^30 erg/s, which is only 20
per cent of the disk luminosity. The rate of accretion onto the white dwarf is
5*10^-12 solar masses per year, about half of the rate in the disk. From the
high-resolution X-ray spectra, we estimate that the X-ray emitting part of the
boundary layer is rotating with a velocity of 540 km/s, which is close the
rotation velocity of the white dwarf but significantly smaller than the
Keplerian velocity. We detect a 60-s quasi-periodic oscillation of the X-ray
flux that is likely due to the rotation of the boundary layer. The X-ray and
the ultra-violet flux show strong variability on a time scale of ~1500 s. We
find that the variability in the two bands is correlated and that the X-ray
fluctuations are delayed by ~100 s. The correlation indicates that the variable
ultra-violet flux is emitted near the transition region between the disk and
the boundary layer and that accretion rate fluctuations in this region are
propagated to the X-ray emitting part of the boundary layer within ~100 s. An
orbital modulation of the X-ray flux suggests that the inner accretion disk is
tilted with respect to the orbital plane. The elemental abundances in the
boundary layer are close to their solar values.
