We present an analysis of X-ray and UV data obtained with the XMM-Newton Observatory of the long period dwarf nova RU Peg .
RU Peg contains a massive white dwarf , possibly the hottest white dwarf in a dwarf nova , it has a low inclination , thus optimally exposing its X-ray emitting boundary layer , and has an excellent trigonometric parallax distance .

We modeled the X-ray data using XSPEC assuming a multi-temperature plasma emission model built from the MEKAL code ( i.e. , CEVMKL ) .
We obtained a maximum temperature of 31.7 keV , based on the EPIC MOS1 , 2 and pn data , indicating that RU Peg has an X-ray spectrum harder than most dwarf novae , except U Gem .
This result is consistent with and indirectly confirms the large mass of the white dwarf in RU Peg .
The X-ray luminosity we computed corresponds to a boundary layer luminosity for a mass accretion rate of 2 \times 10 ^ { -11 } M _ { \odot } /yr ( assuming M _ { wd } = 1.3 M _ { \odot } ) , in agreement with the expected quiescent accretion rate .
The modeling of the O viii emission line at 19Å as observed by the RGS implies a projected stellar rotational velocity v _ { rot } \sin { i } = 695 km ~ { } s ^ { -1 } , i.e .
the line is emitted from material rotating at \sim 936-1245 km ~ { } s ^ { -1 } ( i \sim 34 ^ { \circ } -48 ^ { \circ } ) or about 1/6 of the Keplerian speed ; this velocity is much larger than the rotation speed of the white dwarf inferred from the Far Ultraviolet Spectroscopic Explorer ( FUSE ) spectrum .
Cross-correletion analysis yielded an undelayed ( time lag \sim 0 ) component and a delayed component of 116 \pm 17 sec where the X-ray variations/fluctuations lagged the UV variations .
This indicates that the UV fluctuations in the inner disk are propagated into the X-ray emitting region in about 116 sec .
The undelayed component may be related to irradiation effects .