scholarly journals Infrared photometry of the dwarf nova V2051 Ophiuchi – II. The quiescent accretion disc and its spiral arms

2019 ◽  
Vol 492 (1) ◽  
pp. 1154-1163 ◽  
Author(s):  
Raymundo Baptista ◽  
Eduardo Wojcikiewicz
Keyword(s):  
High Viscosity ◽  
Accretion Disc ◽  
Light Curves ◽  
Light Sources ◽  
Spiral Arms ◽  
Dwarf Nova ◽  
Wave Modulation ◽  
Disc Centre ◽  
Mapping Techniques ◽  
Analysis Of Time Series

ABSTRACT We report the analysis of time-series of infrared JHKs photometry of the dwarf nova  V2051 Oph in quiescence with eclipse mapping techniques to investigate structures and the spectrum of its accretion disc. The light curves after removal of the ellipsoidal variations caused by the mass-donor star show a double-wave modulation signalling the presence of two asymmetric light sources in the accretion disc. Eclipse maps reveal two spiral arms on top of the disc emission, one at $R_1= 0.28\pm 0.02 \, R_\mathrm{L1}$ and the other at $R_2= 0.42\pm 0.02 \, R_\mathrm{L1}$ (where RL1 is the distance from disc centre to the inner Lagrangian point), which are seen face-on at binary phases consistent with the maxima of the double-wave modulation. The wide open angle inferred for the spiral arms (θs = 21° ± 4°) suggests the quiescent accretion disc of V2051 Oph has high viscosity. The accretion disc is hot and optically thin in its inner regions ($T_\mathrm{gas}\sim 10\!-\!12 \times 10^3\, \mathrm{ K}$ and surface densities $\sim 10^{-3}\text{ to }10^{-2}\, \mathrm{ g}\, \mathrm{ cm}^{-2}$), and becomes cool and opaque in its outer regions.

scholarly journals Spectral mapping of V348 Puppis: spiral arms in the period gap★

2016 ◽  
Vol 457 (1) ◽  
pp. 198-211 ◽  
Author(s):  
R. K. Saito ◽  
R. Baptista
Keyword(s):  
Thermal Emission ◽  
Hubble Space Telescope ◽  
Accretion Disc ◽  
Spectral Mapping ◽  
Empirical Expression ◽  
Spiral Arms ◽  
Disc Centre ◽  
Angular Momentum Loss ◽  
Mapping Techniques ◽  
The Continuum

Abstract We report the analysis of Hubble Space Telescope (HST) UV–optical spectroscopy of the nova-like variable V348 Puppis with eclipse mapping techniques. We measured the eclipse width at disc centre and determined a lower limit on the mass ratio of q > 0.3, with a tight relation between q and the binary inclination i. For 0.31 ≤ q ≤ 0.6, we have 79$_{.}^{\circ}$5 ≤ i ≤ 88$_{.}^{\circ}$2. Simulations with 3D eclipse mapping give no support to the suggestion of self-shielding of the accretion disc of V348 Pup, indicating a geometrically thin disc. Eclipse maps reveal two structures in the accretion disc interpreted as tidally induced spiral arms, which account for 50–60  per cent of the disc flux in the continuum. The uneclipsed component accounts for 30–50  per cent of the light, indicating that a significant fraction of the light comes from a vertically extended disc chromosphere + wind. Its spectrum can be fitted by an isothermal slab of gas with temperature T = 9600 K and column density Σ ∼1010 g cm−2, corresponding to optically thick thermal emission. Superhumps had faded by the epoch of the HST observations; the disc shrank in size while the disc wind flux increased with respect to observations when superhumps were present. This may be explained if the disc wind outflow is the dominant source of angular momentum loss from the accretion disc. Previously observed accretion disc radii of V348 Pup and of two other binaries with large discs are used to derive an empirical expression for the maximum possible disc radius, which implies that superhumps may be found in systems with up to q ≃ 0.7.

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 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 SOAR observations of the high-viscosity accretion disc of the dwarf nova V4140 Sagitarii in quiescence and in outburst

2016 ◽  
Vol 463 (4) ◽  
pp. 3799-3812 ◽  
Author(s):  
Raymundo Baptista ◽  
Bernardo W. Borges ◽  
Alexandre S. Oliveira
Keyword(s):  
High Viscosity ◽  
Accretion Disc ◽  
Dwarf Nova

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 Relativistic accretion disc in tidal disruption events

2020 ◽  
Vol 496 (2) ◽  
pp. 1784-1802
Author(s):  
T Mageshwaran ◽  
Sudip Bhattacharyya
Keyword(s):  
Surface Density ◽  
Accretion Disc ◽  
Time Parameter ◽  
Light Curves ◽  
Initial Time ◽  
Late Time ◽  
Tidal Disruption ◽  
Bolometric Luminosity ◽  
Spectral Bands ◽  
Accretion Model

ABSTRACT We construct a time-dependent relativistic accretion model for tidal disruption events (TDEs) with an α-viscosity and the pressure dominated by gas pressure. We also include the mass fallback rate $\dot{M}_\mathrm{ f}$ for both full and partial disruption TDEs, and assume that the infalling debris forms a seed disc in time tc, which evolves due to the mass addition from the infalling debris and the mass-loss via accretion on to the black hole. Besides, we derive an explicit form for the disc height that depends on the angular momentum parameter in the disc. We show that the surface density of the disc increases at an initial time due to mass addition, and then decreases as the mass fallback rate decreases, which results in a decrease in the disc mass Md with a late-time evolution of Md ∝ t−1.05 and t−1.38 for full and partial disruption TDEs, respectively, where t is the time parameter. The bolometric luminosity L shows a rise and decline that follows a power law at late times given by L ∝ t−1.8 and t−2.3 for full and partial disruption TDEs, respectively. Our obtained luminosity declines faster than the luminosity inferred using $L \propto \dot{M}_\mathrm{ f}$. We also compute the light curves in various spectral bands.

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.

Parameters of Dwarf Nova SS Cygni

1997 ◽  
Vol 163 ◽  
pp. 818-819 ◽  
Author(s):  
Irina Voloshina ◽  
Tatjana Khruzina
Keyword(s):  
Light Curves ◽  
Dwarf Nova

AbstractThe analysis of dwarf nova SS Cyg light curves at quiescence is performed and some important are determined.

scholarly journals The May 1985 Superoutburst of OY Carinae: I. Structure of the Outer Disk from Optical and IR Observations

1987 ◽  
Vol 93 ◽  
pp. 365-369
Author(s):  
T. Naylor ◽  
J. Bailey ◽  
F.M. Bateson ◽  
G. Berriman ◽  
P.A. Charles ◽  
...  
Keyword(s):  
Accretion Disk ◽  
Light Curves ◽  
The Other ◽  
Dwarf Nova ◽  
Outer Disk ◽  
Cool Region

AbstractWe present optical and IR observations of the dwarf nova OY Car during the May 1985 superoutburst. From them we find that the superhump has a temperature of ~8000K and an area of order half the size of the red dwarf or accretion disk. We also compare the behaviour during two simultaneous optical/IR observations. Whilst the light curves in the two pass bands are similar during one observation, in the other observation they show marked differences that may be due to a cool region in the outer disk.

scholarly journals Superoutbursts and Superhumps of SU UMa Stars

1988 ◽  
Vol 108 ◽  
pp. 238-239
Author(s):  
Yoji Osaki ◽  
Masahito Hirose
Keyword(s):  
Accretion Disk ◽  
Orbital Period ◽  
White Dwarf ◽  
Binary Systems ◽  
Roche Lobe ◽  
Light Curves ◽  
Close Binary ◽  
Dwarf Novae ◽  
Dwarf Nova ◽  
Close Binary Systems

SU UMa stars are one of subclasses of dwarf novae. Dwarf novae are semi-detached close binary systems in which a Roche-lobe filling red dwarf secondary loses matter and the white dwarf primary accretes it through the accretion disk. The main characteristics of SU UMa subclass is that they show two kinds of outbursts: normal outbursts and superoutbursts. In addition to the more frequent narrow outbursts of normal dwarf nova, SU UMa stars exhibit “superoutbursts”, in which stars reach about 1 magnitude brighter and stay longer than in normal outburst. Careful photometric studies during superoutburst have almost always revealed the “superhumps”: periodic humps in light curves with a period very close to the orbital period of the system. However, the most curious of all is that this superhump period is not exactly equal to the orbital period, but it is always longer by a few percent than the orbital period.

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