Accretion Geometry of Synchronously Rotating Magnetic Cataclysmic Variables: Theories versus Observations

1994 ◽  
Vol 11 (2) ◽  
pp. 198-200 ◽  
Author(s):  
Kinwah Wu ◽  
D. T. Wickramasinghe ◽  
J. Bailey ◽  
A. F. Tennant
Keyword(s):  
Magnetic Field ◽  
White Dwarf ◽  
Cataclysmic Variables ◽  
Quadrupole Field ◽  
Companion Star ◽  
Magnetic Cataclysmic Variables ◽  
Theoretical Results

AbstractWe review the magnetic locking of the white dwarf and the companion star in AM Herculis-type binaries for various white dwarf magnetic field structures, and compare the theoretical results with observations. The model in which the white dwarf has a dipole plus a quadrupole field is found to be in closest agreement with the recent observations.

scholarly journals Eclipsing AM Herculis Binaries

1997 ◽  
Vol 163 ◽  
pp. 391-395
Author(s):  
Jeremy Bailey
Keyword(s):  
Magnetic Field ◽  
Strong Magnetic Field ◽  
Time Resolution ◽  
White Dwarf ◽  
Cataclysmic Variables ◽  
High Time ◽  
High Time Resolution ◽  
Companion Star ◽  
Fundamental Properties ◽  
Cyclotron Radiation

AbstractAM Herculis Binaries (or Polars) are a subclass of the Cataclysmic Variables in which the accreting white dwarf has a strong magnetic field giving rise to highly polarized cyclotron radiation from the shock heated accretion region. A number of AM Herculis binaries are now known in which the white dwarf is eclipsed by the companion star. High time resolution observations of these eclipses allow a particularly detailed study of the process of accretion onto the magnetic white dwarf. Results on a number of systems will be presented and used to derive information on the accretion structure as well as on the fundamental properties of the binaries.

scholarly journals The EUV Excess in Magnetic Cataclysmic Variables

1996 ◽  
Vol 152 ◽  
pp. 325-329
Author(s):  
John K. Warren ◽  
Koji Mukai
Keyword(s):  
Magnetic Field ◽  
Orbital Period ◽  
White Dwarf ◽  
Preliminary Analysis ◽  
Cataclysmic Variables ◽  
X Rays ◽  
System Parameters ◽  
Magnetic Capture ◽  
Magnetic Cataclysmic Variables ◽  
Capture Radius

We present preliminary analysis of EUVE pointed data of 8 magnetic cataclysmic variables. Blackbody temperatures, luminosities, and interstellar columns have been better constrained. Using these luminosities we look for correlations between the EUV excess (over optical and hard X-rays) and various system parameters. While it appears there is no correlation between the EUV excess and the system inclination and orbital period, correlations are suggested between the EUV excess and the longitude of the accretion spot, the colatitude of the accretion spot, the white dwarf magnetic field, and the magnetic capture radius.

scholarly journals Extreme Ultraviolet Spectroscopy of Magnetic Cataclysmic Variables

1996 ◽  
Vol 152 ◽  
pp. 309-316
Author(s):  
Frits Paerels ◽  
Min Young Hur ◽  
Christopher W. Mauche
Keyword(s):  
High Resolution ◽  
White Dwarf ◽  
Extreme Ultraviolet ◽  
Cataclysmic Variables ◽  
Ultraviolet Spectroscopy ◽  
Temperature Structure ◽  
Polar Cap ◽  
Ultraviolet Emission ◽  
X Ray ◽  
Magnetic Cataclysmic Variables

A longstanding problem in the interpretation of the X-ray and extreme ultraviolet emission from strongly magnetic cataclysmic variables can be addressed definitively with high resolution EUV spectroscopy. A detailed photospheric spectrum of the accretion-heated polar cap of the white dwarf is sensitive in principle to the temperature structure of the atmosphere. This may allow us to determine where and how the bulk of the accretion energy is thermalized. The EUVE data on AM Herculis and EF Eridani are presented and discussed in this context.

scholarly journals Winds from Disks

1990 ◽  
Vol 122 ◽  
pp. 228-235
Author(s):  
J.E. Drew
Keyword(s):  
Magnetic Field ◽  
Numerical Modelling ◽  
Mass Loss ◽  
Weak Magnetic Field ◽  
Cataclysmic Variables ◽  
Dwarf Novae ◽  
Loss Mechanism ◽  
Fundamental Cause ◽  
Magnetic Cataclysmic Variables ◽  
Thermonuclear Runaway

The disks referred to in the title of this paper are specifically those present in cataclysmic variables in which the accreting white dwarf has a relatively weak magnetic field (≪ 1 MG). Such systems are classified either as nova-like variables or as dwarf novae, and are of interest here because they are believed to be novae in quiescence (Ritter and Livio discuss this point elsewhere in this volume).This review aims to do two things: i) to summarise what has been learned about the winds associated with non-magnetic cataclysmic variables both from observation and from numerical modelling, and ii) to outline ideas about the nature of the mass loss mechanism. By contrast with the certainty that nova outflows are the consequence of thermonuclear runaway, it shall be seen that the fundamental cause of mass loss from cataclysmic variables remains obscure. An earlier review of this subject is by Cordova and Howarth (1986). Also of interest are some sections of the monograph on dwarf novae and nova-like variables by LaDous (1989).

scholarly journals Masses and Magnetic Fields of White Dwarfs in Cataclysmic Variables

1989 ◽  
Vol 114 ◽  
pp. 337-340
Author(s):  
J.P. Lasota ◽  
J.M. Hameury ◽  
A.R. King
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Magnetic Fields ◽  
White Dwarf ◽  
White Dwarfs ◽  
Cataclysmic Variables ◽  
Strong Support ◽  
Drastic Reduction ◽  
Secondary Star ◽  
Maximum Magnetic Field

We show that the existence of the AM Her period spike implies (i) a unique white dwarf mass ≃ 0.6 − 0.7M⊙ for most magnetic CV’s (ii) nova explosions remove exactly the accreted mass from magnetic white dwarfs, and (iii) the maximum magnetic field for most CV’s is ≤ 4 × 107 G. The existence of the spike is very strong support for the idea that the period gap results from a drastic reduction of angular momentum losses when the secondary star becomes fully convective.

scholarly journals Radiation-hydrodynamic Models of the Accretion Spots in Magnetic Cataclysmic Variables

2004 ◽  
Vol 190 ◽  
pp. 187-200 ◽  
Author(s):  
K. Beuermann
Keyword(s):  
Mass Flux ◽  
White Dwarf ◽  
Cataclysmic Variables ◽  
Strong Shock ◽  
Hydrodynamic Models ◽  
Mass Fluxes ◽  
Open Questions ◽  
Low Mass ◽  
Magnetic Cataclysmic Variables ◽  
Theoretical Foundations

AbstractThe structure of the near-polar accretion spots on accreting magnetic white dwarfs has been studied theoretically and observationally in numerous papers over the last decade. Detailed treatments are available for the regime of low mass flux, usually termed the bombardment case, and for higher mass fluxes which create a strong shock standing above the photosphere of the white dwarf. No general treatment is so far available for the case of shocks buried deep in the photosphere. I review the theoretical foundations, present some applications of theory, and discuss in short the open questions which still need to be addressed.

scholarly journals The Spin Periods of Magnetic Cataclysmic Variables

2004 ◽  
Vol 190 ◽  
pp. 216-229 ◽  
Author(s):  
A. J. Norton ◽  
R. V. Somerscales ◽  
G. A. Wynn
Keyword(s):  
Orbital Period ◽  
Magnetic Moment ◽  
White Dwarf ◽  
Magnetic Moments ◽  
Cataclysmic Variables ◽  
Intermediate Polars ◽  
Magnetic Cataclysmic Variables ◽  
Remarkable Agreement

AbstractWe have used a model of magnetic accretion to investigate the rotational equilibria of magnetic cataclysmic variables (MCVs). This has enabled us to derive a set of equilibrium spin periods as a function of orbital period and magnetic moment which we use to estimate the magnetic moments of all known intermediate polars. We further show how these equilibrium spin periods relate to the polar synchronisation condition and use these results to calculate the theoretical histogram describing the distribution of magnetic CVs as a function of Pspin/Porb. We demonstrate that this is in remarkable agreement with the observed distribution assuming that the number of systems as a function of white dwarf magnetic moment is distributed according to .

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