XMM–Newton observation of MV Lyr and the sandwiched model confirmation

Abstract

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.

Similar shot profile morphology of fast variability in a cataclysmic variable, X-ray binary, and blazar: The MV Lyrae case

“…Finally, Borisov (1992) and Skillman et al (1995) together with Kraicheva et al (1999) found a QPO at a period near 47 minutes. The corresponding frequency of log(f /Hz) = -3.45 is in perfect agreement with one PDS component detected by Scaringi et al (2012a) in the optical Kepler data and by Dobrotka et al (2017) in the X-ray XMM-Newton light curve. This power excess is also seen in the simulations (Fig.…”

“…If the variability is generated by the corona radiating hard X-rays, the optical Kepler data is a result of the reprocessing of the X-rays, and the corresponding PDS component must be detected in X-rays too. This interpretation was confirmed by XMM-Newton observations (Dobrotka et al 2017) where two highest PDSs components were detected.…”

“…Such a corona radiates in X-rays, and this radiation is reprocessed by the geometrically thin accretion disc resulting in detected optical radiation. This was confirmed by the XMM-Newton observation by Dobrotka et al (2017) yielding a presence of the log(f /Hz) ≃ −3 component in an X-rays PDS 10 . It suggests a very low mass accretion rate typical for dwarf novae in quiescence, which is not typical for a high state of a nova like rather resembling dwarf nova in outburst.…”

“…As a next step we searched for the same component in XMM-Newton data. We took the PN light curve from Dobrotka et al (2017). We performed the same lomb-Scargle calculation as in the previous cases, but we rebined the averaged periodogram into larger bins (interval of 0.1 in log scale), and with a minimum number of averaged points of 5 (upper panel of Fig.…”

What We Learn from the X-Ray Grating Spectra of Nova SMC 2016

“…This approach is suitable to study quasi periodic oscillations (QPOs) or red noise. We estimated the PDS as in Dobrotka et al (2017), i.e. we split the light curve into n div subsamples (subdivision in time ranges), then we calculated periodograms in log-log space for every subsample, averaged them and finally binned the data in equally spaced bins if a minimum number of points per bin is fulfilled (otherwise the bin is larger).…”