scholarly journals Super-Eddington accretion in the Q2237+0305 quasar?

2021 ◽  
Vol 645 ◽  
pp. A78
Author(s):  
L. A. Berdina ◽  
V. S. Tsvetkova ◽  
V. M. Shulga
Keyword(s):  
Accretion Disk ◽  
Light Curves ◽  
Time Lags ◽  
Disk Model ◽  
Spectral Bands ◽  
Disk Size ◽  
Supercritical Accretion ◽  
Analytical Expressions

The interband time lags between the flux variations of the Q2237+0305 quasar have been determined from light curves in the Johnson-Cousins V, R, and I spectral bands. The values of the time lags for filter pairs R − V, I − R, and I − V are significantly higher than those predicted by the standard accretion disk model by Shakura and Sunyaev. To explain the discrepancy, the idea of a supercritical accretion regime in quasars considered in 1973 by Shakura and Sunyaev is applied. This regime has been shown by them to cause an extended scattering envelope around the accretion disk. The envelope efficiently scatters and re-emits the radiation from the accretion disk and thus increases the apparent disk size. We made use of analytical expressions for the envelope radius and temperature derived by Shakura and Sunyaev in their analysis of super-Eddington accretion and show that our results are consistent with the existence of such an envelope. The corresponding parameters of the accretion regime were calculated. They provide the radii of the envelope in the V, R, and I spectral bands consistent with the inter-band time lags determined in our work.

scholarly journals THE EFFECT OF A TIME-VARYING ACCRETION DISK SIZE ON QUASAR MICROLENSING LIGHT CURVES

2010 ◽  
Vol 718 (2) ◽  
pp. 1079-1084 ◽  
Author(s):  
Jeffrey A. Blackburne ◽  
Christopher S. Kochanek
Keyword(s):  
Accretion Disk ◽  
Light Curves ◽  
Time Varying ◽  
Disk Size

scholarly journals Quasar Variability: New Surveys and New Models

2002 ◽  
Vol 184 ◽  
pp. 351-356 ◽  
Author(s):  
M.R.S. Hawkins
Keyword(s):  
Accretion Disk ◽  
Structure Functions ◽  
Light Curves ◽  
Monitoring Programme ◽  
Line Of Sight ◽  
Current Interest ◽  
Disk Model ◽  
Large Sample ◽  
New Models ◽  
Quasar Variability

AbstractIn this paper results from a monitoring programme of a large sample of quasars comprising regular yearly observations over a period of 23 years are presented. Structure functions of the light curves are calculated and compared with predictions for models of quasar variability of current interest. These include recently published models of varibility from accretion disk instability, variability from starbursts or supernovae, and variations caused by the microlensing effect of compact bodies along the line of sight. The analysis favours the accretion disk model for low luminosity AGN, but suggests that the variations of more luminous quasars are dominated by microlensing.

scholarly journals Broad-Band Variability in Accreting Compact Objects

2015 ◽  
Vol 2 (1) ◽  
pp. 107-110 ◽  
Author(s):  
S. Scaringi
Keyword(s):  
Accretion Disk ◽  
Broad Band ◽  
Cataclysmic Variables ◽  
Compact Object ◽  
Variable Stars ◽  
Compact Objects ◽  
Time Lags ◽  
Disk Model ◽  
X Ray ◽  
X Ray Binaries

Cataclysmic variable stars are in many ways similar to X-ray binaries. Both types of systems possess an accretion disk, which in most cases can reach the surface (or event horizon) of the central compact object. The main difference is that the embedded gravitational potential well in X-ray binaries is much deeper than those found in cataclysmic variables. As a result, X-ray binaries emit most of their radiation at X-ray wavelengths, as opposed to cataclysmic variables which emit mostly at optical/ultraviolet wavelengths. Both types of systems display aperiodic broad-band variability which can be associated to the accretion disk. Here, the properties of the observed X-ray variability in XRBs are compared to those observed at optical wavelengths in CVs. In most cases the variability properties of both types of systems are qualitatively similar once the relevant timescales associated with the inner accretion disk regions have been taken into account. The similarities include the observed power spectral density shapes, the rms-flux relation as well as Fourier-dependant time lags. Here a brief overview on these similarities is given, placing them in the context of the fluctuating accretion disk model which seeks to reproduce the observed variability.

scholarly journals Accretion Disk Size Measurement and Time Delays in the Lensed Quasar WFI 2033–4723

2018 ◽  
Vol 869 (2) ◽  
pp. 106 ◽  
Author(s):  
Christopher W. Morgan ◽  
Gregory E. Hyer ◽  
Vivien Bonvin ◽  
Ana M. Mosquera ◽  
Matthew Cornachione ◽  
...  
Keyword(s):  
Accretion Disk ◽  
Time Delays ◽  
Size Measurement ◽  
Disk Size

scholarly journals CVs Around the Minimum Orbital Period

2015 ◽  
Vol 2 (1) ◽  
pp. 41-45
Author(s):  
S. Zharikov ◽  
G. Tovmassian
Keyword(s):  
Accretion Disk ◽  
Accretion Disks ◽  
Orbital Period ◽  
Cataclysmic Variables ◽  
Outer Edge ◽  
Light Curves ◽  
Mass Ratio ◽  
Period Limit ◽  
Bounce Back ◽  
The Continuum

We discussed features of Cataclysmic Variables at the period minimum. In general, most of them must be WZ Sge-type objects. Main characteristics of the prototype star (WZ Sge) are discussed. A part of WZ Sge-type objects has evolved past the period limit and formed the bounce back systems. We also explore conditions and structure of accretion disks in such systems. We show that the accretion disk in a system with extreme mass ratio grows in size reaching a 2:1 resonance radius and are relatively cool. They also become largely optically thin in the continuum, contributing to the total flux less than the stellar components of the system. In contrast, the viscosity and the temperature in spiral arms formed at the outer edge of the disk are higher and their contribution in continuum plays an increasingly important role. We model such disks and generate light curves which successfully simulate the observed double-humped light curves in the quiescence.

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.

2.9. Microlens mapping of disks in active galactic nuclei

1998 ◽  
Vol 184 ◽  
pp. 75-76 ◽  
Author(s):  
A. Yonehara ◽  
S. Mineshige ◽  
J. Fukue ◽  
M. Umemura ◽  
E.L. Turner
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Accretion Disk ◽  
Central Region ◽  
Galactic Nuclei ◽  
Direct Information ◽  
Supermassive Black Hole ◽  
Disk Size

Generally, it is believed that there is a supermassive black hole and a surrounding accretion disk in a central region of active galactic nuclei (AGN). However, it is quite difficult to obtain direct information about the center of AGN, because the accretion disk size is far too small to resolve.

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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