scholarly journals A systematic study of spiral density waves in the accretion discs of cataclysmic variables

2019 ◽  
Vol 491 (2) ◽  
pp. 2217-2253
Author(s):  
R Ruiz-Carmona ◽  
P J Groot ◽  
D Steeghs
Keyword(s):  
Systematic Study ◽  
Cataclysmic Variables ◽  
Variable Stars ◽  
Spiral Waves ◽  
Compact Objects ◽  
Accretion Discs ◽  
Density Waves ◽  
Ordered Structures ◽  
System Parameters ◽  
Spiral Density Waves

ABSTRACT Spiral density waves are thought to be excited in the accretion discs of accreting compact objects, including cataclysmic variable stars (CVs). Observational evidence has been obtained for a handful of systems in outburst over the last two decades. We present the results of a systematic study searching for spiral density waves in CVs, and report their detection in two of the sixteen observed systems. While most of the systems observed present asymmetric, non-Keplerian accretion discs during outburst, the presence of ordered structures interpreted as spiral density waves is not as ubiquitous as previously anticipated. From a comparison of systems by their system parameters it appears that inclination of the systems may play a major role, favouring the visibility and/or detection of spiral waves in systems seen at high inclination.

scholarly journals The propagation and absorption of spiral density waves

1970 ◽  
Vol 38 ◽  
pp. 323-325 ◽  
Author(s):  
F. H. Shu
Keyword(s):  
Angular Momentum ◽  
Group Velocity ◽  
Wave Energy ◽  
Radial Direction ◽  
Wave Action ◽  
Spiral Waves ◽  
Stellar Disk ◽  
Density Waves ◽  
Spiral Density Waves

An ‘anti-spiral theorem’ holds with limited validity for the neutral modes of oscillation in a stellar disk - namely, whenever the effects of stellar resonances can be ignored. In the regions between Lindblad resonances, a group of spiral waves will propagate in the radial direction with the group velocity found by Toomre. This propagation occurs with the conservation of ‘wave action’, wave energy, and wave angular momentum.

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.

Models of Cataclysmic Variables from Photometric and Spectroscopic Data

1979 ◽  
Vol 46 ◽  
pp. 65-74 ◽  
Author(s):  
A.C. Fabian ◽  
J.E. Pringle ◽  
J.A.J. Whelan ◽  
J.A. Bailey
Keyword(s):  
Spectroscopic Data ◽  
Cataclysmic Variables ◽  
System Parameters ◽  
Dwarf Nova ◽  
Spectroscopic Observations ◽  
Photometric And Spectroscopic Observations

Abstract.Recent photometric and spectroscopic observations of the dwarf nova system Z Cha are discussed. Methods for constraining the system parameters are applied and the disc emissivity is deduced as a function of radius. Indications are found that the disc shrinks in size with increasing time after outburst.

ON THE POSSIBILITY OF FORMING ACCRETION INDUCED COLLAPSE IN MASSIVE CATACLYSMIC VARIABLES

2013 ◽  
Vol 23 ◽  
pp. 284-288
Author(s):  
ALI TAANI ◽  
MASHHOOR AL-WARDAT ◽  
YONGHENG ZHAO
Keyword(s):  
Cataclysmic Variables ◽  
Compact Objects ◽  
Significant Fraction ◽  
Formation And Evolution ◽  
Orbital Periods ◽  
Chandrasekhar Limit

We investigate the process of Accretion Induced Collapse (AIC) during the evolution of massive Cataclysmic Variables (CVs) type binaries, which possibly to occur in our galaxy. The relation between spin periods and orbital periods in different nature of compact objects in binaries, is investigated. We study also the implication and application of the AIC process of the MSPs population. We conclude that a significant fraction of MSPs may originate from AIC (4 - 40%). Hence, massive CVs are of key importance for the formation and evolution of binary MSPs, once they reach the Chandrasekhar limit then collapse to becomes an NS, or blow as apart in a supernova, consequently impart significant kick to the companion and creating long orbital periods. In some cases, this process disrupts the system and creates a single MSP.

Tidal Excitation of Spiral Waves in Accretion Discs

1994 ◽  
pp. 363-374
Author(s):  
G. J. Savonije ◽  
J. C. B. Papaloizou ◽  
D. N. C. Lin
Keyword(s):  
Spiral Waves ◽  
Accretion Discs

scholarly journals Professional/Amateur Cooperation in the Study of Variable Stars as Illustrated by the Fourth Edition of the GCVS

1988 ◽  
Vol 98 ◽  
pp. 188-189
Author(s):  
M.S. Frolov
Keyword(s):  
Classical Group ◽  
Cataclysmic Variables ◽  
Variable Stars ◽  
Eclipsing Binaries ◽  
Fourth Edition ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Long Time ◽  
Hand Involvement ◽  
Lyrae Stars

Let us divide variable stars into two main groups: the first “classical” group, includes objects known for a long time, such as Cepheids, RR-Lyrae stars, Miras, cataclysmic variables, eclipsing binaries, etc. The second group includes micropulsating variables of δ Scuti and β Cephei types, magnetic variables, rotating variables of BY Draconis type, etc.Historically, the contribution of amateurs in investigating the first group was very significant, and it continues to increase. On the other hand, involvement in studying the second group of stars was practically equal to zero some years ago, but today one can see the beginnings of an expansion of amateur work on this second group of variables – among brighter objects, of course. One reason is the beginning of cooperation between amateurs and professional astronomers having powerful instruments.

scholarly journals Star Formation in Normal Irregular Galaxies

1987 ◽  
Vol 115 ◽  
pp. 611-612
Author(s):  
Deidre A. Hunter
Keyword(s):  
Star Formation ◽  
Large Range ◽  
Density Waves ◽  
Regulatory Processes ◽  
Spiral Density Waves ◽  
Global Properties ◽  
Level Of Activity ◽  
Star Formation Activity ◽  
Irregular Galaxies

Normal, non-interacting irregular galaxies can be quite successful at forming stars. Therefore, spiral density waves are not necessary to a vigorous production of stars. Nevertheless, there is a large range in star-formation rates among irregular galaxies. Irregulars with common characteristics can have different overall levels of star-formation activity, so that the level of activity does not seem to be simple related to observable global properties of galaxian systems. The constant star formation rates of most normal irregulars also imply the existence of regulatory processes.

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