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

Abstract

Context. The cataclysmic variable MV Lyr was present in the Kepler field yielding a light curve with the duration of almost 1500 days with 60 second cadence. Such high quality data of this nova-like system with obvious fast optical variability show multicomponent power density spectra as shown previously by Scaringi et al.Aims. Our goal is to study the light curve from different point of view, and perform a shot profile analysis. We search for characteristics not discovered with standard power density spectrum based methods. Methods. The shot profile method identifies individual shots in the light curve, and averages them in order to get all substructures with typical time scales. We also tested the robustness of our analysis using simple shot noise model. Although, the principle of this method is not totally physically correct, we use it as a purely phenomenological approach. Results. We obtained mean profiles with multicomponent features. The shot profile method distinguishes substructures with similar time scales which appear as a single degenerate feature in power density spectra. Furthermore, this method yields the identification of another high frequency component in the power density spectra of Kepler and XMM-Newton data not detected so far. Moreover, we found side-lobes accompanied with the central spike, making the profile very similar to another Kepler data of blazar W2R 1926+42, and Ginga data of Cyg X-1. All three objects show similar time scale ratios of the rising vs. declining part of the central spikes, while the two binaries have also similar rising profiles of the shots described by a power-law function.Conclusions. The similarity of both binary shot profiles suggests that the shots originate from the same origin, e.g. aperiodic mass accretion in the accretion disc. Moreover, the similarity with the blazar may imply that the ejection fluctuations in the blazar jet are connected to accretion fluctuations driving the variability in binaries. This points out to connection between jet and the accretion disc.

Alternation of the flickering morphology between the high and low state in MV Lyrae

“…The two remaining high frequency components were also detected in X-rays by Dobrotka et al (2017), facilitating any discussion and interpretation. We also searched for an additional high frequency component that is also of X-ray origin (Dobrotka et al 2019).…”

“…In light of this, as an additional study of the variability morphology we performed the same superposed shot profile analysis as Dobrotka et al (2019). The goal was to "see directly" individual PDS components in the flare shape, like in the case of Cyg X-1 (Negoro et al 2001).…”

“…In the second step, the flare extension must be defined, in this case as N ptsext points to the left and to the right from the peak. Like in Dobrotka et al (2019), we used N ptsext = N pts /2 in order not to superimpose a declining branch of one flare onto a rising branch of the adjacent flare, and vice versa.…”

“…This is the case of the dominant PDS feature at log( f /Hz) = −3. Dobrotka et al (2019) performed a superposed shot profile analysis (method based on Negoro et al 1994) of the fast variability, and found that both the central spike and side lobes produce a PDS pattern very close to log( f /Hz) = −3. If this PDS component is variable, the standard PDS study can not resolve substructures in which the shot profile is responsible for the variability.…”

“…A very similar profile was found by Sasada et al (2017) using Kepler data of the blazar W2R 1926+42, but on a much longer timescale. The third object showing such a multicomponent flare shape with a central spike and side-lobes is MV Lyr (Dobrotka et al 2019) with a timescale between the X-ray binary and the blazar. All three findings make the situation very interesting because of the very different nature of all three objects.…”