Fast stochastic variability study of two SU UMa systems V1504 Cyg and V344 Lyr observed by<i>Kepler</i>satellite

Dobrotka, A.; Ness, J. U.; Bajčičáková, Ingrida

doi:10.1093/mnras/stw1001

Cited by 16 publications

(20 citation statements)

References 25 publications

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“…Therefore, such transition region can be highly turbulent. A similar interpretation was proposed by Dobrotka et al (2016) in the case of V1504 Cyg and V344 Lyr, where a break frequency in the optical PDS is seen during outburst, but absent during quiescence. The disc is developed down to the white dwarf surface in the former case, while it is absent in the latter.…”

Section: Proposed Modelsupporting

confidence: 80%

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

Dobrotka

Ness

Mineshige

et al. 2017

Monthly Notices of the Royal Astronomical Society

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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.

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Section: Proposed Modelsupporting

confidence: 80%

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

Dobrotka

Ness

Mineshige

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…(b) From Table 2 of . (c) From Table 2 of Dobrotka et al (2016). (d) From Dobrotka et al ( 2014) (e) From Balman & Revnivtsev (2012).…”

Section: Discussionmentioning

confidence: 99%

“…Knowledge of the presence of PDS components in Kepler data of CVs at frequencies close to the values determined in this paper is not new. and Dobrotka et al (2016) studied PDSs of two dwarf novae present in the Kepler field, V1504 Cyg and V344 Lyr. Both systems show the PDS behaving in a similar way depending on the activity stage.…”

Section: Analogy With X-ray Binariesmentioning

confidence: 99%

“…The existence of the accretion process is usually seen as fast stochastic variability (also known as flickering). Flickering has three very basic observational characteristics; (1) linear correlation between variability amplitude and log-normally distributed flux (so-called rms-flux relation) observed in all varieties of accreting systems (see, e.g., Scaringi et al 2012b; Van de Sande et al 2015 for CVs case), (2) character of red noise or band limited noise with characteristic frequencies in power density spectra (PDS, see, e.g., Scaringi et al 2012a;Dobrotka et al 2014Dobrotka et al , 2016 for CVs case), and (3) time lags where flares reach their maxima slightly earlier in the blue than in the red (Scaringi et al 2013;Bruch 2015) An alternative method to "see" the PDS components was proposed by Negoro et al (1994). The authors superposed many flares (shots) from the Ginga light curve of the X-ray binary Cyg X-1 in order to get a mean profile showing all typical stable features, like the central spike and the two sidelobes on both sides of the spike.…”

Section: Introductionmentioning

confidence: 99%

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

Dobrotka

Negoro

Konopka³

2020

A&A

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Aims. We studied unique data of the nova-like system MV Lyr taken by the Kepler space telescope during its transition from the high to low state and vice versa. We were interested in the evolution of frequency components found previously in different data also obtained by Kepler. Methods. We divided the light curve into ten-day segments and investigated the corresponding power density spectra. We searched for individual frequency components by fitting with Lorentzian functions. Additionally, we investigated the variability using averaged shot profiles calculated from the light curve divided into ten equally spaced subsamples. Results. We found very complex changes in the power density spectra. We focused our study onto three frequency components. A significant increase in activity is seen at low frequencies. Contrariwise, the high frequency part of the spectrum strongly decreases in power with a specific rise in characteristic frequencies of the individual components. We discuss various scenarios of this phenomenology such as the reprocessing of X-rays in a receding accretion disk or radiation from a more active region at the outer disk. Finally, we show that various cataclysmic variables show similar characteristic frequencies in their power density spectra. These are dependent on activity stage, making the situation similar to X-ray binaries.

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“…V447 Lyr was seen to show eclipses, short outburst and long outbursts [252]. V344 Lyr and V1504 Cyg have been the subjects of multiple studies [253,254]. A new CV was found during the K2 mission, as a variable background star to the F-dwarf EPIC 203830112 [255].…”

Section: Evolved Binariesmentioning

confidence: 99%

Space-Based Photometry of Binary Stars: From Voyager to TESS

Southworth

2021

Universe

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Binary stars are crucial laboratories for stellar physics, so have been photometric targets for space missions beginning with the very first orbiting telescope (OAO-2) launched in 1968. This review traces the binary stars observed and the scientific results obtained from the early days of ultraviolet missions (OAO-2, Voyager, ANS, IUE), through a period of diversification (Hipparcos, WIRE, MOST, BRITE), to the current era of large planetary transit surveys (CoRoT, Kepler, TESS). In this time observations have been obtained of detached, semi-detached and contact binaries containing dwarfs, sub-giants, giants, supergiants, white dwarfs, planets, neutron stars and accretion discs. Recent missions have found a huge variety of objects such as pulsating stars in eclipsing binaries, multi-eclipsers, heartbeat stars and binaries hosting transiting planets. Particular attention is paid to eclipsing binaries, because they are staggeringly useful, and to the NASA Transiting Exoplanet Survey Satellite (TESS) because its huge sky coverage enables a wide range of scientific investigations with unprecedented ease. These results are placed into context, future missions are discussed, and a list of important science goals is presented.

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Fast stochastic variability study of two SU UMa systems V1504 Cyg and V344 Lyr observed byKeplersatellite

Cited by 16 publications

References 25 publications

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

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

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

Space-Based Photometry of Binary Stars: From Voyager to TESS

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