scholarly journals FS Aur as a Permanent Superhump System

2004 ◽  
Vol 194 ◽  
pp. 169-171
Author(s):  
Gaghik H. Tovmassian ◽  
Sergei V. Zharikov
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Variable Mass ◽  
Accretion Disc ◽  
Light Curves ◽  
Cataclysmic Variable ◽  
Short Period ◽  
Photometric Period ◽  
Low Amplitude

AbstractWe discovered that the short period cataclysmic variable FS Aur at some epochs shows a photometric period close to the orbital. It exceeds the orbital period by ∽2%, which is a sign of the presence of a permanent superhump in the system. Superhumps tend to appear near short, low amplitude outbursts. We assume that FS Aur possesses a large thermally stable accretion disc and that the outburst may be due to the variable mass transfer rate. This, however, does not alter our previous explanation of yet another, 2.4 times longer than orbital, photometric period of FS Aur, found earlier, and persistently observed in its light curves.

scholarly journals A Beat Phenomenon in Dwarf Nova Eruptions

1977 ◽  
Vol 42 ◽  
pp. 227-233
Author(s):  
N. Vogt
Keyword(s):  
Mass Transfer ◽  
Orbital Period ◽  
Transfer Rate ◽  
Convection Zone ◽  
Mass Transfer Rate ◽  
Accretion Disc ◽  
Light Curves ◽  
Dwarf Nova ◽  
Beat Phenomenon ◽  
Photoelectric Observations

Photoelectric observations of the dwarf nova VW Hyi, obtained at the end of the December 1975 supermaximum, are presented. After decline from the outburst, the superhump period (0ḍ07622) combines with the orbital period (0ḍ07427) to a beat phenomenon: the O-C’s and the light curves of the orbital hump vary systematically with the phase of the beat period for at least one week after recovery from the supermaximum. It is suggested that the red secondary component, which rotates non-synchroneously with the superhump period, expands slightly at the beginning of a supermaximum and is heated up asymmetrically, probably due to instabilities in its convection zone. In addition, the increased mass transfer rate may trigger the long eruption in the accretion disc while short eruptions originate in the disc without participation of the secondary.

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 Irregular X-ray Variation of LMC X-3

1995 ◽  
Vol 151 ◽  
pp. 336-337
Author(s):  
H.C. Pan ◽  
G.K. Skinner ◽  
R.A. Sunyaev ◽  
N.L. Alexandrovich
Keyword(s):  
Mass Transfer ◽  
Energy Range ◽  
Spectral Resolution ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Space Station ◽  
Large Magellanic Cloud ◽  
Accretion Disc ◽  
X Ray ◽  
Coded Mask

LMC X-3 is an X-ray binary in the Large Magellanic Cloud. It was discovered by UHURU and observations with various satellites showed that the X-ray source was variable by a factor of up to 100 (e.g. Traves et al. 1988). Using the GINGA and HEAO-1 observations, Cowley et al. (1991) found a strong ∼ 198 (or possibly ∼ 99) day modulation in the X-ray luminosities of LMC X-3. They suggested that this modulation may be due to an accretion disc precession, or periodic variations in the mass transfer rate, or a combination of both.We observed LMC X-3 with the TTM in 1988-1990. The present paper gives some results from the analysis of the data obtained.The TTM is a coded mask telescope on board the MIR space station. It is capable of producing images in the energy range 2-30 keV with a spectral resolution of about 18% at 6 keV (Brinkman et al. 1985).

scholarly journals The New View on the Long-Therm Flickering in T CrB

2004 ◽  
Vol 194 ◽  
pp. 235-235
Author(s):  
A. Dobrotka ◽  
L. Hric ◽  
K. Petrík
Keyword(s):  
Mass Transfer ◽  
Light Curve ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Variable Mass ◽  
Lagrangian Point ◽  
Turbulent Eddies ◽  
Theoretical Assumptions ◽  
Powerful Flare

The big scatter of data on the light curve of T CRB is identified with the flickering activity of the system. The data performed during April 1996 have a falling trend and they can be a part of a downward branch of a long-term and energetically powerful flare. Estimated energy 2 1035 J and the duration of this event were compared with the theoretical assumptions based on three typical physical scenarios, which can be the source of flickering. The dissipation of magnetic loops and the existence of the turbulent eddies are energetically deficient, but these scenarios are real in the case of less powerfull flares. The real explanation could be the instability of the secondary and variable mass transfer rate through the Lagrangian point, therefore through whole disc.

scholarly journals IM Normae: The Death Spiral of a Cataclysmic Variable?

2022 ◽  
Vol 924 (1) ◽  
pp. 27
Author(s):  
Joseph Patterson ◽  
Jonathan Kemp ◽  
Berto Monard ◽  
Gordon Myers ◽  
Enrique de Miguel ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Light Curves ◽  
High Rate ◽  
High Mass ◽  
Cataclysmic Variable ◽  
Short Period ◽  
Accretion Rates ◽  
Low Mass ◽  
Recurrent Nova ◽  
Cataclysmic Variable Evolution

Abstract We present a study of the orbital light curves of the recurrent nova IM Normae since its 2002 outburst. The broad “eclipses” recur with a 2.46 hr period, which increases on a timescale of 1.28(16) × 106 yr. Under the assumption of conservative mass transfer, this suggests a rate near 10−7 M ⊙ yr−1, and this agrees with the estimated accretion rate of the postnova, based on our estimate of luminosity. IM Nor appears to be a close match to the famous recurrent nova T Pyxidis. Both stars appear to have very high accretion rates, sufficient to drive the recurrent-nova events. Both have quiescent light curves, which suggest strong heating of the low-mass secondary, and very wide orbital minima, which suggest obscuration of a large “corona” around the primary. And both have very rapid orbital period increases, as expected from a short-period binary with high mass transfer from the low-mass component. These two stars may represent a final stage of nova—and cataclysmic variable—evolution, in which irradiation-driven winds drive a high rate of mass transfer, thereby evaporating the donor star in a paroxysm of nova outbursts.

scholarly journals A Model for WZ Sge with “Standard” Values of α

1997 ◽  
Vol 163 ◽  
pp. 279-282 ◽  
Author(s):  
J.M. Hameury ◽  
J.M. Huré ◽  
J.P. Lasota
Keyword(s):  
Mass Transfer ◽  
Thermal Equilibrium ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Accretion Disc ◽  
Recurrence Time ◽  
Equilibrium Curve ◽  
Standard Values ◽  
Inner Parts ◽  
Standard Disc

AbstractWe present a model for the dwarf nova WZ Sge which does not imply an unusually – and unexplained – low value of the viscosity during low states. We propose that the inner parts of the accretion disc are disrupted by either a magnetic field or evaporation, so that the disc is stable (or very close to being stable) in quiescence, as the mass transfer rate is very low, and the disc can sit on the cool, lower branch of the thermal equilibrium curve. Outbursts are triggered by an increase of mass transfer, causing a standard disc instability, and are strongly enhanced by illumination effects. Both the recurrence time, and the characteristics of the light curve in outburst can be accounted for.

scholarly journals VY Sculptoris stars are Magnetic Cataclysmic Variables

2004 ◽  
Vol 190 ◽  
pp. 46-52 ◽  
Author(s):  
Jean-Pierre Lasota ◽  
Jean-Marie Hameury
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Magnetic Moments ◽  
Mass Transfer Rate ◽  
Cataclysmic Variables ◽  
Accretion Disc ◽  
Intermediate States ◽  
Intermediate Polars ◽  
Magnetic Cataclysmic Variables ◽  
Evolutionary Aspects

AbstractWe show that VY Scl stars must be magnetized in order to account for the absence of outbursts during their low and intermediate states. Absence of outbursts during low states requires only rather low magnetic moments but in systems in which the drops and rises of luminosity are slower than it takes for the accretion disc to adjust viscously to the variation in mass-transfer rate preventing outbursts require magnetic moments of Intermediate Polars. We discuss some evolutionary aspects of this conclusion.

scholarly journals Testing the disk instability model of cataclysmic variables

2018 ◽  
Vol 617 ◽  
pp. A26 ◽  
Author(s):  
Guillaume Dubus ◽  
Magdalena Otulakowska-Hypka ◽  
Jean-Pierre Lasota
Keyword(s):  
Mass Transfer ◽  
Orbital Period ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Sampling Rate ◽  
Cataclysmic Variables ◽  
Irregular Sampling ◽  
Light Curves ◽  
Stable Region ◽  
Dwarf Novae

Context. The disk instability model (DIM) attributes the outbursts of dwarf novae to a thermal-viscous instability of their accretion disk, an instability to which nova-like stars are not subject. Aims. We aim to test the fundamental prediction of the DIM: the separation of cataclysmic variables (CVs) into nova-likes and dwarf novae depending on orbital period and mass transfer rate from the companion. Methods. We analyzed the light curves from a sample of ≈130 CVs with a parallax distance in the Gaia DR2 catalog to derive their average mass transfer rate. We validated the method for converting optical magnitude to mass accretion rate against theoretical light curves of dwarf novae. Results. Dwarf novae (resp. nova-likes) are consistently placed in the unstable (resp. stable) region of the orbital period – mass transfer rate plane predicted by the DIM. None of the analyzed systems present a challenge to the model. These results are robust against the possible sources of error and bias that we investigated. Light curves from Kepler or, in the future, the LSST or Plato surveys, could alleviate a major source of uncertainty, that is, the irregular sampling rate of the light curves, assuming good constraints can be set on the orbital parameters of the CVs that they happen to target. Conclusions. The disk instability model remains the solid basis on which to construct an understanding of accretion processes in CVs.

scholarly journals New Observational Frontiers of ER UMa (= PG 0943+521) Type Dwarf Novae

1996 ◽  
Vol 158 ◽  
pp. 59-60
Author(s):  
D. Nogami ◽  
T. Kato ◽  
S. Masuda ◽  
R. Hirata ◽  
K. Matsumoto ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Natural Extension ◽  
Light Curves ◽  
Recurrence Time ◽  
Dwarf Novae ◽  
Recurrence Times ◽  
Tidal Torque ◽  
Duty Cycles

The ER UMa-type, including ER UMa, V1159 Ori and RZ LMi, is a subgroup of SU UMa-type dwarf novae. Outbursts of these stars are characterized by: (i) the extremely short recurrence time of the superoutburst (~ 40 d in ER UMa and V1159 Ori, ~ 20 d in RZ LMi), (ii) short outbursts with short recurrence times (~ 4 d) between the bright states, and (iii) extremely long duty cycles (~ 0.5). Assuming that the mass transfer rate from the secondary is ten times higher than that of ordinary SU UMa stars, which was invoked by Kato & Kunjaya (1995), and a weak tidal torque in the case of RZ LMi, Osaki (1996) showed that the light curves of these stars can be reproduced by the disk instability model, which does not require mass transfer bursts. These indicate that ER UMa, V1159 Ori and RZ LMi are not on the natural extension of SU UMa-type dwarf novae.

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