2014A&A...566A.121N

WZ Sagittae is the prototype object of a subclass of dwarf novae with rare and long (super)outbursts, in which a white dwarf primary accretes matter from a low mass companion. High-energy observations offer the possibility of a better understanding of the disk-accretion mechanism in WZ Sge-like binaries. We used archival XMM-Newton and Swift data to characterize the X-ray spectral and temporal properties of WZ Sge in quiescence. We performed a detailed timing analysis of the simultaneous X-ray and UV light curves obtained with the EPIC and OM instruments on board XMM-Newton in 2003. We employed several techniques in this study, including a correlation study between the two curves. We also performed an X-ray spectral analysis using the EPIC data and Swift/XRT data obtained in 2011. We find that the X-ray intensity is clearly modulated at a period of ≃28.96s, confirming previously published preliminary results. We find that the X-ray spectral shape of WZ Sge remains practically unchanged between the XMM-Newton and Swift observations. However, after correcting for interstellar absorption, the intrinsic luminosity is estimated to be L^Una_X=(2.65±0.06)x10³⁰erg/s and L^Una_X=(1.57±0.03)x10³⁰erg/s in 2003 and 2011, respectively. During the Swift/XRT observation, the observed flux is a factor ≃2 lower than that observed by XMM-Newton but is similar to the quiescent levels that are observed various times before the 2001 outburst.