scholarly journals Is There Observational Evidence for the Evaporation of the Inner Accretion Disk in Dwarf Novae at Quiescence?

1996 ◽  
Vol 158 ◽  
pp. 81-84
Author(s):  
C. La Dous ◽  
E. Meyer-Hofmeister ◽  
F. Meyer
Keyword(s):  
Accretion Disk ◽  
Strong Evidence ◽  
Observational Evidence ◽  
Dwarf Novae ◽  
Evaporation Model ◽  
Preliminary Results ◽  
Theoretical Predictions

AbstractWe present the preliminary results of a comparison of observed general patterns of quiescent dwarf novae and theoretical predictions of the disk evaporation model. We demonstrate that, even though details still have to be clarified, on the whole there is strong evidence that observations and theory are in agreement.

scholarly journals IUE Observations of WZ Sagittae in Outburst

1980 ◽  
Vol 88 ◽  
pp. 447-451 ◽  
Author(s):  
Albert V. Holm ◽  
Chi-Chao Wu ◽  
Warren M. Sparks ◽  
Francis H. Schiffer ◽  
Albert Boggess
Keyword(s):  
Accretion Disk ◽  
The Sun ◽  
Dwarf Novae ◽  
Low Resolution ◽  
Preliminary Results ◽  
International Ultraviolet Explorer ◽  
Recurrent Nova

The International Ultraviolet Explorer was used to obtain spectra at both 7 Å and 0.2 Å resolution of the recurrent nova WZ Sagittae during its 1978 outburst. The first spectra were obtained on 1978 Dec 1.8 UT, approximately 0.7 days after discovery. The decay from outburst was followed until 1979 Jan 1, after which it was too near the Sun to be observed. A post-outburst spectrum was obtained on 1979 July 11. In this paper, preliminary results from the analysis of the low resolution spectra are discussed. These observations will be used to support the similarity between WZ Sge and dwarf novae and to test accretion disk models.

scholarly journals Ultraviolet Observations of Cataclysmic Variables

1987 ◽  
Vol 93 ◽  
pp. 205-205 ◽  
Author(s):  
F. Verbunt
Keyword(s):  
Orbital Period ◽  
Cataclysmic Variables ◽  
Type Systems ◽  
Terminal Velocity ◽  
Dwarf Novae ◽  
Preliminary Results ◽  
System Type ◽  
International Ultraviolet Explorer ◽  
Flux Level ◽  
Ultraviolet Observations

AbstractThe preliminary results of the analysis of more than 1000 spectra of cataclysmic variables in the archive of the International Ultraviolet Explorer were presented at the meeting. To characterize the slope of the spectra I use F = log(f1460Å/f2880Å). For most spectra F lies between 0.2 and 0.7. No correlation of F with orbital period, inclination, system type or (for dwarf novae) length of the interoutburst interval are found, apart from somewhat lower values of F for DQ Her type systems. Out of 16 dwarf novae for which spectra both at outburst maximum and minimum are available 11 show no large difference in F between maximum and minimum, and in 5 F declines with the flux level. Out of 6 dwarf novae 5 show very red spectra during the rise to maximum, and 1 shows slopes during rise similar to those during decline.In the ultraviolet resonance lines, due to a wind from the disc, no correlation is found between inclination and terminal velocity.

scholarly journals Techniques and Results of Observations of Rapid and Ultrarapid Variable Stars

1971 ◽  
Vol 15 ◽  
pp. 144-159 ◽  
Author(s):  
Brian Warner
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
Variable Stars ◽  
Observational Evidence ◽  
Short Time Scale ◽  
Dwarf Novae ◽  
Stellar Objects ◽  
Blue Object ◽  
Flare Stars ◽  
Short Time

The inception of the present era of interest in rapidly varying stars may be identified with M. F. WALKER’s discovery in 1954 (WALKER 1954) of changes in the brightness of the blue object MacRae+43° 1 (now known as MVLyr), on a time scale of a few minutes. Outside of flare stars, few other stellar objects were suspected to vary on such a short time scale. GREENSTEIN’s (1954) spectra showed that MV Lyr resembles an old nova, which stimulated WALKER to look for light fluctuations in old, recurrent, and dwarf novae and related stars. His observational evidence that all members of these classes show variations of various amplitudes and time scales is summarized in the IAU Colloquium on non-stable stars (WALKER 1957). Most spectacular of his discoveries was the existence of 71 sec periodic variations in the light from the remnant of Nova Herculis 1934 (DQ Her) (WALKER 1956).

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.

scholarly journals Dynamo Action in Accretion Disks

1993 ◽  
Vol 157 ◽  
pp. 209-210
Author(s):  
Ulf Torkelsson
Keyword(s):  
Numerical Simulations ◽  
Accretion Disk ◽  
Accretion Disks ◽  
Standard Theory ◽  
Dynamo Action ◽  
Preliminary Results

Employing the standard theory for thin accretion disks I estimate the relevant parameters for a dynamo in an accretion disk. These estimates could then be compared to the results of numerical simulations. Some preliminary results of such simulations (Torkelsson & Brandenburg 1992) are presented too.

scholarly journals Preliminary Results of Improved Model Fits to the Extreme and Far UV Observations of Cataclysmic Variables

1987 ◽  
Vol 93 ◽  
pp. 239-242
Author(s):  
T.E. Carone ◽  
R.S. Polidan ◽  
R.A. Wade
Keyword(s):  
Steady State ◽  
Accretion Disk ◽  
Cataclysmic Variables ◽  
Flux Ratio ◽  
Preliminary Results ◽  
First Results ◽  
Improved Model ◽  
Model Fits

AbstractWe present the first results of a study which will attempt to analyze the combined Voyager and IUE observations of cataclysmic variables using steady-state accretion disk models. Initially we use flux ratio diagrams to determine if a combination of models will suffice or if new ingredients are necessary.

scholarly journals Fuse Studies of Dwarf Novae during Quiescence

2004 ◽  
Vol 194 ◽  
pp. 194-195
Author(s):  
E. M. Sion ◽  
F. H. Cheng ◽  
P. Godon ◽  
P. Szkody
Keyword(s):  
Boundary Layer ◽  
White Dwarf ◽  
White Dwarfs ◽  
Disk Accretion ◽  
Dwarf Novae ◽  
Preliminary Results ◽  
Accretion Physics

AbstractWe have obtained FUSE spectra of several dwarf novae which reveal the properties of their accreting white dwarfs, their rates of accretion during quiescence and the nature of their boundary layer/inner disk regions including accretion belts on the white dwarfs. Among the systems for which preliminary results will be presented are BV Cen, WW Ceti, EY Cyg, SS Aur and VW Hyi. The contribution of these FUSE studies to our understanding of disk accretion physics will be emphasized within the context of the white dwarf and boundary layer.

New Results on Double Charmonium Production in e+e- Annihilation at $\sqrt{s} \approx 10.6~{\rm GeV}$ with the Belle Detector

2005 ◽  
Vol 20 (16) ◽  
pp. 3617-3620
Author(s):  
◽  
T. Ziegler
Keyword(s):  
Cross Section ◽  
Strong Evidence ◽  
Previous Analysis ◽  
Charmonium State ◽  
Data Set ◽  
Charmonium Production ◽  
Belle Detector ◽  
Theoretical Predictions ◽  
Order Of Magnitude ◽  
The Cross

Extending a previous analysis1 the double charmonium production [Formula: see text] and [Formula: see text] has been investigated with a data set of 155 fb-1 with the Belle detector. Theoretical predictions for the cross section are one order of magnitude lower than the measured value and this discrepancy is still not understood. In a very recent update with a dataset of 285 fb-1 strong evidence for a new charmonium state at a mass of 3.940 GeV was found.

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