Related papers: Radiation from Dwarf Nova Discs
We report the results of a systematic comparison between the vertically averaged model and the vertically explicit model of steady state, Keplerian, optically thick "alpha"-discs. The simulations have concerned discs currently found in…
Context. Although the disc instability model is widely accepted as the explanation for dwarf nova outbursts, it is still necessary to confront its predictions to observations because much of the constraints on angular momentum transport in…
We analyse simultaneous UBVR quiescent light curves of the cataclysmic variable V2051 Oph using the Physical Parameter Eclipse Mapping method in order to map the gas temperature and surface density of the disc for the first time. The disc…
We present an analysis of the FUSE spectra of eight high-declination dwarf novae obtained from a Cycle 7 FUSE survey. These DN systems have not been previously studied in the UV and little is known about their white dwarfs (WDs) or…
We estimate a value of the viscosity parameter in AGN accretion discs for the PG quasar sample. We assume that optical variability on time-scales of months to years is caused by local instabilities in the inner accretion disc. Comparing the…
We report on time series of CCD photometry of V4140 Sgr between 1991 and 2001. The analysis reveals that the object was in the decline from an outburst in 1992 and again in outburst in 2001. The historical light curve collected by amateur…
X-ray spectra of dwarf novae in quiescence observed by Chandra and XMM-Newton provide new information on the boundary layers of their accreting white dwarfs. Comparison of observations and models allows us to extract estimates for the…
We have analysed a series of Suzaku data and one dataset of XMM-Newton of the SU UMa type dwarf nova VW Hyi in optical quiescence. The observed spectra in the 0.2-10 keV band are moderately well represented by multi-temperature thermal…
We present dynamically consistent solutions for hot accretion onto unmagnetized, rotating white dwarfs (WDs) in five quiescent dwarf novae. The measured WD rotation rates (and other system parameters) in RX And, SS Cyg, U Gem, VW Hyi and WZ…
The tomographic method "Physical Parameter Eclipse Mapping" is a tool to reconstruct spatial distributions of physical parameters (like temperatures and surface densities) in accretion discs of cataclysmic variables. After summarizing the…
I review models trying to explain dwarf-nova outbursts and soft X-ray transients. The disc-instability model for dwarf-novae is still in its preliminary state of development: its predictions depend very strongly on the unknown viscosity…
Physical mechanism responsible for high viscosity in accretion disks is still under debate. Parameterization of the viscous stress as $\alpha P$ proved to be a successful representation of this mechanism in the outer parts of the disk,…
We address the task of modeling soft X-ray and optical light curves of X-ray novae in the high/soft state. The analytic model of viscous evolution of an externally truncated accretion \alpha-disk is used. Relativistic effects near a Kerr…
We describe the results of numerical simulations of the dynamics of the boundary layer (BL) between the accretion disk and the surface of a non-magnetic white dwarf (WD) for different viscosities which corresponds to different stages for…
The eruptive cycles of dwarf novae (DN) are thought to be due to a thermal-viscous instability in the accretion disk surrounding the white dwarf (WD). This model has long been known to imply a stress to pressure ratio \alpha ~0.1 in…
This study inspects the light and radial-velocity curves of the eclipsing binary AV Del. In comparison with other studies already done, the study shows that the absolute elements, fundamental orbital and physical parameters of the system…
We consider observational and theoretical estimates of the accretion disc viscosity parameter $\alpha$. We find that in thin, fully-ionized discs, the best observational evidence suggests a typical range $\alpha \sim 0.1 - 0.4$, whereas the…
Numerical, two-dimensional, time-dependent hydrodynamical models of geometrically thick accretion discs around black holes are presented. Accretion flows with non-effective radiation cooling (ADAFs) can be both convectively stable or…
Using a 2.5D time-dependent axisymmetric numerical code we recently developed, we solve the full compressible Navier-Stokes equations (including an alpha-viscosity prescription) to determine the structure of the boundary layer between the…
We report the analysis of 22 B-band light curves of the dwarf nova V4140 Sgr obtained with SOI/SOAR during two nights along the decline of a superoutburst in 2006 Sep 12-24 and in quiescence over 50 days following the superoutburst.…