scholarly journals On the evolution of accretion disc flow in cataclysmic variables - II. The existence and nature of collective relaxation oscillations in dwarf nova systems

1983 ◽  
Vol 205 (2) ◽  
pp. 487-513 ◽  
Author(s):  
J. Papaloizou ◽  
J. Faulkner ◽  
D. N. C. Lin
Keyword(s):  
Cataclysmic Variables ◽  
Accretion Disc ◽  
Relaxation Oscillations ◽  
Dwarf Nova

scholarly journals Rapid Keck Spectroscopy of Cataclysmic Variables

2004 ◽  
Vol 194 ◽  
pp. 155-157
Author(s):  
Warren Skidmore ◽  
Keith Horne ◽  
Kevin Pearson ◽  
Richard Gomer ◽  
Kieran O'Brien ◽  
...  
Keyword(s):  
Cataclysmic Variables ◽  
Accretion Disc ◽  
Dwarf Nova ◽  
Different Types

Abstract We present an analysis of Rapid Keck Spectroscopy of the CVs AM Her (polar) and SS Cyg (dwarf nova). We decompose the spectra into constant and variable components and identify different types of variability in AM Her with different characteristic timescales. The variable flickering component of the accretion disc flux md the observational characteristics of a small flare in SS Cyg are isolated.

Models of Cataclysmic Variables from Photometric and Spectroscopic Data

1979 ◽  
Vol 46 ◽  
pp. 65-74 ◽  
Author(s):  
A.C. Fabian ◽  
J.E. Pringle ◽  
J.A.J. Whelan ◽  
J.A. Bailey
Keyword(s):  
Spectroscopic Data ◽  
Cataclysmic Variables ◽  
System Parameters ◽  
Dwarf Nova ◽  
Spectroscopic Observations ◽  
Photometric And Spectroscopic Observations

Abstract.Recent photometric and spectroscopic observations of the dwarf nova system Z Cha are discussed. Methods for constraining the system parameters are applied and the disc emissivity is deduced as a function of radius. Indications are found that the disc shrinks in size with increasing time after outburst.

scholarly journals Accretion-disc model spectra for dwarf-nova stars

2010 ◽  
Vol 519 ◽  
pp. A117 ◽  
Author(s):  
I. Idan ◽  
J.-P. Lasota ◽  
J.-M. Hameury ◽  
G. Shaviv
Keyword(s):  
Accretion Disc ◽  
Dwarf Nova ◽  
Disc Model

scholarly journals Theory of Dwarf Novae

1976 ◽  
Vol 73 ◽  
pp. 173-192
Author(s):  
G. T. Bath
Keyword(s):  
Mass Transfer ◽  
Steady State ◽  
Recent Work ◽  
Accretion Disc ◽  
Optical Behaviour ◽  
Dwarf Novae ◽  
Physical Processes ◽  
Dwarf Nova ◽  
Theoretical Results

Recent work on the physical processes resulting from mass transfer between the red and blue components of dwarf nova binaries is reviewed. The optical behaviour of the blue component's accretion disc suggests that it may be the infall, accretion energy which is being liberated during outbursts. Theoretical results which suggest that the red component may suffer quasi-periodic mass transfer instabilities are discussed. The resulting accretion disc properties are considered and compared with the observed optical outburst behaviour for the simplest steady state disc models. The complexity of the interaction between the two stellar components in these systems is emphasized.

scholarly journals The disappearance and reformation of the accretion disc during a low state of FO Aquarii

2017 ◽  
Vol 606 ◽  
pp. A7 ◽  
Author(s):  
J.-M. Hameury ◽  
J.-P. Lasota
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Hot Spot ◽  
Mass Transfer Rate ◽  
Accretion Disc ◽  
Numerical Code ◽  
Light Sources ◽  
Instability Strip ◽  
Dwarf Nova ◽  
Nova Outbursts

Context. FO Aquarii, an asynchronous magnetic cataclysmic variable (intermediate polar) went into a low state in 2016, from which it slowly and steadily recovered without showing dwarf nova outbursts. This requires explanation since in a low state, the mass-transfer rate is in principle too low for the disc to be fully ionised and the disc should be subject to the standard thermal and viscous instability observed in dwarf novae. Aims. We investigate the conditions under which an accretion disc in an intermediate polar could exhibit a luminosity drop of two magnitudes in the optical band without showing outbursts. Methods. We use our numerical code for the time evolution of accretion discs, including other light sources from the system (primary, secondary, hot spot). Results. We show that although it is marginally possible for the accretion disc in the low state to stay on the hot stable branch, the required mass-transfer rate in the normal state would then have to be extremely high, of the order of 1019 g s-1 or even larger. This would make the system so intrinsically bright that its distance should be much larger than allowed by all estimates. We show that observations of FO Aqr are well accounted for by the same mechanism that we have suggested as explaining the absence of outbursts during low states of VY Scl stars: during the decay, the magnetospheric radius exceeds the circularisation radius, so that the disc disappears before it enters the instability strip for dwarf nova outbursts. Conclusions. Our results are unaffected, and even reinforced, if accretion proceeds both via the accretion disc and directly via the stream during some intermediate stages; the detailed process through which the disc disappears still requires investigation.

scholarly journals Pulsating white dwarfs in cataclysmic variables: The marriage of ZZ Cet and dwarf nova

2004 ◽  
Vol 193 ◽  
pp. 382-386 ◽  
Author(s):  
Brian Warner ◽  
Patrick A. Woudt
Keyword(s):  
White Dwarf ◽  
Large Amplitude ◽  
White Dwarfs ◽  
Cataclysmic Variables ◽  
Sloan Digital Sky Survey ◽  
Dwarf Novae ◽  
Dwarf Nova ◽  
Sky Survey

AbstractThere are now four dwarf novae known with white dwarf primaries that show large amplitude non-radial oscillations of the kind seen in ZZ Cet stars. We compare the properties of these stars and point out that by the end of the Sloan Digital Sky Survey more than 30 should be known.

scholarly journals Optical spectra of FO Aquarii during low and high accretion rates

2020 ◽  
Vol 495 (4) ◽  
pp. 4445-4462
Author(s):  
M R Kennedy ◽  
P M Garnavich ◽  
C Littlefield ◽  
T R Marsh ◽  
P Callanan ◽  
...  
Keyword(s):  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Cataclysmic Variables ◽  
Accretion Disc ◽  
High State ◽  
Secondary Star ◽  
Accretion Rates ◽  
Magnetic Poles ◽  
The Impact ◽  
Impact Region

ABSTRACT Between 2016 May and 2018 September, the intermediate polar (IP) FO Aquarii exhibited two distinct low states and one failed low state. We present optical spectroscopy of FO Aquarii throughout this period, making this the first detailed study of an accretion disc during a low state in any IP. Analysis of these data confirm that the low states are the result of a drop in the mass transfer rate between the secondary star and the magnetic white dwarf primary, and are characterized by a decrease in the system’s brightness coupled with a change of the system’s accretion structures from an accretion disc-fed geometry to a combination of disc-fed and ballistic stream-fed accretion, and that effects from accretion on to both magnetic poles become detectable. The failed low state only displays a decrease in brightness, with the accretion geometry remaining primarily disc-fed. We also find that the WD appears to be exclusively accretion disc-fed during the high state. There is evidence for an outflow close to the impact region between the ballistic stream and the disc which is detectable in all of the states. Finally, there is marginal evidence for narrow high-velocity features in the H α emission line during the low states which may arise due to an outflow from the WD. These features may be evidence of a collimated jet, a long predicted yet elusive feature of cataclysmic variables.

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