On the Correlated X‐Ray and Optical Evolution of SS Cygni

McGowan, K.; Priedhorsky, W. C.; Trudolyubov, S.

doi:10.1086/380758

Cited by 41 publications

(52 citation statements)

References 21 publications

(36 reference statements)

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“…Schreiber et al (2003) showed that an increased X-ray flux is expected at the onset of an every outburst when the mass accretion rate is rising and while the BL is still in an optically thin state, and at its end, when the mass accretion rate decreases below a critical value of the order of 10 16 g s −1 and the BL transitions to its optically thin state. Surprisingly, however, a temporary increase at both the beginning and end of outbursts was observed previously only in SS Cyg and GW Lib (Wheatley et al 2003;McGowan et al 2004;Byckling et al 2009). …”

Section: Transition Of the Accretion Disc From Optically Thick To Optmentioning

confidence: 52%

Superhumps linked to X-ray emission

Neustroev

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Kuulkers

et al. 2018

A&A

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The superoutbursts of SSS J122221.7−311525 and GW Lib. ABSTRACTContext. We present more than 4 years of Swift X-ray observations of the 2013 superoutburst, subsequent decline and quiescence of the WZ Sge-type dwarf nova SSS J122221.7−311525 (SSS J122222) from 6 days after discovery. Aims. Only a handful of WZ Sge-type dwarf novae have been observed in X-rays, and until recently GW Lib was the only binary of this type with complete coverage of an X-ray light curve throughout a superoutburst. We collected extensive X-ray data of a second such system to understand the extent to which the unexpected properties of GW Lib are common to the WZ Sge class. Methods. We collected 60 Swift-XRT observations of SSS J122222 between 2013 January 6 and 2013 July 1. Four follow-up observations were performed in 2014, 2015, 2016 and 2017. The total exposure time of our observations is 86.6 ks. We analysed the X-ray light curve and compared it with the behaviour of superhumps which were detected in the optical light curve. We also performed spectral analysis of the data. The results were compared with the properties of GW Lib, for which new X-ray observations were also obtained. Results. SSS J122222 was variable and around five times brighter in 0.3-10 keV X-rays during the superoutburst than in quiescence, mainly because of a significant strengthening of a high-energy component of the X-ray spectrum. The post-outburst decline of the X-ray flux lasted at least 500 d. The data show no evidence of the expected optically thick boundary layer in the system during the outburst. SSS J122222 also exhibited a sudden X-ray flux change in the middle of the superoutburst, which occurred exactly at the time of the superhump stage transition. A similar X-ray behaviour was also detected in GW Lib. Conclusions. We show that the X-ray flux exhibits changes at the times of changes in the superhump behaviour of both SSS J122222 and GW Lib. This result demonstrates a relationship between the outer disc and the white dwarf boundary layer for the first time, and suggests that models for accretion discs in high mass ratio accreting binaries are currently incomplete. The very long decline to X-ray quiescence is also in strong contrast to the expectation of low viscosity in the disc after outburst.

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Section: Transition Of the Accretion Disc From Optically Thick To Optmentioning

confidence: 52%

Superhumps linked to X-ray emission

Neustroev

Page

Kuulkers

et al. 2018

A&A

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“…This is because the X-ray luminosities are much higher than is consistent with a low-state disc extending down to the white dwarf surface (e.g. Lasota 2001;Wheatley, Mauche & Mattei 2003) and because the accretion rates are seen to decrease rather than increase between outbursts (McGowan et al 2004;Collins & Wheatley 2010;Fer-tig et al 2011). These observations tend to support the suggestions that the inner disc is eroded in the low state.…”

Section: X-ray Luminositiesmentioning

confidence: 97%

Distances of cataclysmic variables and related objects derived fromGaiaData Release 1

Ramsay

Schreiber

Gänsicke

et al. 2017

A&A

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We consider the parallaxes of sixteen cataclysmic variables and related objects that are included in the TGAS catalogue, which is part of the Gaia first data release, and compare these with previous parallax measurements. The parallax of the dwarf nova SS Cyg is consistent with the parallax determination made using the VLBI, but with only one of the analyses of the HST Fine Guidance Sensor (FGS) observations of this system. In contrast, the Gaia parallaxes of V603 Aql and RR Pic are broadly consistent, but less precise than the HST/FGS measurements. The Gaia parallaxes of IX Vel, V3885 Sgr, and AE Aqr are consistent with, but much more accurate than the Hipparcos measurements. We take the derived Gaia distances and find that absolute magnitudes of outbursting systems show a weak correlation with orbital period. For systems with measured X-ray fluxes we find that the X-ray luminosity is a clear indicator of whether the accretion disc is in the hot and ionised or cool and neutral state. We also find evidence for the X-ray emission of both low and high state discs correlating with orbital period, and hence the long-term average accretion rate. The inferred mass accretion rates for the nova-like variables and dwarf novae are compared with the critical mass accretion rate predicted by the Disk Instability Model. While we find agreement to be good for most systems there appears to be some uncertainty in the system parameters of SS Cyg. Our results illustrate how future Gaia data releases will be an extremely valuable resource in mapping the evolution of cataclysmic variables.

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“…The spectra of some dwarf novae and the light curves of eclipsing systems in various energy ranges also point to the absence of a part of the optically thick accretion disk inside a region with a size of several white dwarf radii (see e.g., Schoembs and Vogt, 1981;Berriman et al, 1985;Polidan and Carone, 1987;Wood et al, 1992;Hoard et al, 1997;La Dous et al, 1997;Gänsicke et al, 1999;Bíró, 2000;McGowan et al, 2004;Hartley et al, 2005;Belle et al, 2005;Linnell et al, 2007;Puebla et al, 2007;Revnivtsev et al, 2010).…”

Section: Accretion Flow In Dwarf Novaementioning

confidence: 99%

Peculiarities of the accretion flow in the system HL CMa

et al. 2016

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The properties of the aperiodic brightness variability for the dwarf nova HL CMa are considered. The variability of the system HL CMa is shown to be suppressed at frequencies above 7 × 10 −3 Hz. Different variability suppression mechanisms related to the radiation reprocessing time, partial disk evaporation, and characteristic variability formation time are proposed. It has been found that the variability suppression frequency does not change when the system passes from the quiescent state to the outburst one, suggesting that the accretion flow geometry is invariable. It is concluded from the optical and X-ray luminosities of the system that the boundary layer on the white dwarf surface is optically thick in both quiescent and outburst states. The latter implies that the optically thick part of the accretion flow (disk) reaches the white dwarf surface. The accretion rate in the system, the flow geometry and temperature have been estimated from the variability power spectra and spectral characteristics in a wide energy range, from the optical to X-ray.

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On the Correlated X‐Ray and Optical Evolution of SS Cygni

Cited by 41 publications

References 21 publications

Superhumps linked to X-ray emission

Superhumps linked to X-ray emission

Distances of cataclysmic variables and related objects derived fromGaiaData Release 1

Peculiarities of the accretion flow in the system HL CMa

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