086037

V630 Cas is one of several long-period cataclysmic variables with rare comma long-duration comma dwarf nova outbursts. The characteristics of these outbursts are likely shaped by the large physical size of the accretion disks. Moreover comma they often are luminous openPar> 10e33 ergs-sclosePar X-ray sources in quiescence comma severely challenging the disk instability model. Here we propose an XMM-Newton observation of V630 Cas in quiescence to constrain the white dwarf mass and the accretion rate comma possibly adding it to the list of troubling systems with a high accretion rate white dwarf with a large comma quiescent accretion disk. We also propose to obtain fast UV photometry with the OM comma since UV flickering is a key diagnostic of accretion for the related class of symbiotic stars.