We present spectral and timing analyses of simultaneous X-ray and UV observations of the VY Scl system MV Lyr taken by XMM-Newton , containing the longest continuous X-ray+UV light curve and highest signal-to-noise X-ray ( EPIC ) spectrum to date .
The RGS spectrum displays emission lines plus continuum , confirming model approaches to be based on thermal plasma models .
We test the sandwiched model based on fast variability that predicts a geometrically thick corona that surrounds an inner geometrically thin disc .
The EPIC spectra are consistent with either a cooling flow model or a 2-T collisional plasma plus Fe emission lines in which the hotter component may be partially absorbed which would then originate in a central corona or a partially obscured boundary layer , respectively .
The cooling flow model yields a lower mass accretion rate than expected during the bright state , suggesting an evaporated plasma with a low density , thus consistent with a corona .
Timing analysis confirms the presence of a dominant break frequency around log ( f /Hz ) = -3 in the X-ray Power Density Spectrum ( PDS ) as in the optical PDS .
The complex soft/hard X-ray light curve behaviour is consistent with a region close to the white dwarf where the hot component is generated .
The soft component can be connected to an extended region .
We find another break frequency around log ( f /Hz ) = -3.4 that is also detected by Kepler .
We compared flares at different wavelengths and found that the peaks are simultaneous but the rise to maximum is delayed in X-rays with respect to UV .