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.

SPIN PERIODICITY MEASUREMENTS OF WHITE DWARFS HOSTED IN SOUTHERN HARD X–RAY INTERMEDIATE POLAR CANDIDATES

2010 ◽  
Vol 19 (06) ◽  
pp. 797-803
Author(s):  
ILEANA ANDRUCHOW ◽  
NICOLA MASETTI ◽  
DOMITILLA DE MARTINO ◽  
SERGIO A. CELLONE ◽  
ELENA MASON ◽  
...  
Keyword(s):  
Optical Spectroscopy ◽  
White Dwarf ◽  
Preliminary Analysis ◽  
Cataclysmic Variables ◽  
Optical Spectra ◽  
X Rays ◽  
Optical Photometry ◽  
X Ray ◽  
Orbital Periods ◽  
Magnetic Cataclysmic Variables

Thanks to the combination of hard X–ray data afforded with the INTEGRAL satellite and optical spectroscopy at various telescopes, a number of new, possibly magnetic, Cataclysmic Variables (CVs) has been recently discovered. We here report on the preliminary analysis of B-band optical photometry performed with the 2.15m "Jorge Sahade" telescope at CASLEO (Argentina) on 5 CVs discovered at hard X–rays with INTEGRAL and which show features of a magnetic white dwarf (WD) in their optical spectra. The aim of these observations is to derive the orbital periods of these systems and the spin periodicity of their accreting WD.

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 .

scholarly journals Time Dependence in Accretion Onto Magnetic White Dwarfs

1983 ◽  
Vol 72 ◽  
pp. 199-205
Author(s):  
Steven H. Langer ◽  
G. Chanmugam ◽  
G. Shaviv
Keyword(s):  
Magnetic Field ◽  
Kinetic Energy ◽  
Orbital Period ◽  
White Dwarf ◽  
Velocity Structure ◽  
Theoretical Models ◽  
Cataclysmic Variable ◽  
X Rays ◽  
Accretion Flow ◽  
The Magnetic Field

In this talk, we consider cataclysmic variable systems containing a white dwarf with a strong magnetic field. These include systems like AM Her (see, e.g., Chiappetti, Tanzi, and Treves 1981) in which the white dwarf rotates at the orbital period and systems such as AE Aquari in which the white dwarf rotates much faster than synchronously (see Patterson et al. 1980). The magnetic field in all of these systems is strong enough to disrupt the accretion disk at a point far above the surface of the white dwarf and may prevent the formation of a disk altogether. We will present theoretical models for the temperature, density, and velocity structure of the accretion flow in the region near the surface of the white dwarf where the kinetic energy of the flow is thermalized and radiated in the form of X-rays and ultraviolet radiation. This information is required to calculate accurate model spectra, and the results also have immediate consequences for the interpretation of observations.

scholarly journals ROSAT observations of non-magnetic CVs

1996 ◽  
Vol 158 ◽  
pp. 273-276 ◽  
Author(s):  
A. van Teeseling ◽  
F. Verbunt ◽  
K. Beuermann
Keyword(s):  
Boundary Layer ◽  
Accretion Disk ◽  
White Dwarf ◽  
Accretion Rate ◽  
Cataclysmic Variables ◽  
Rotation Velocity ◽  
X Rays ◽  
X Ray ◽  
Orbital Modulation ◽  
Magnetic Cataclysmic Variables

In non-magnetic cataclysmic variables the accreted matter forms an accretion disk around the white dwarf. In the boundary layer between the white dwarf and the accretion disk the accreted matter decelerates from Keplerian velocities to the rotation velocity of the white dwarf. If the accretion rate is high the boundary layer would be optically thick and cool (T ~ 105K), and if the accretion rate is low the boundary layer would be optically thin and hot (T ~ 108K) (Pringle & Savonije 1979).There are several observational problems with this simple picture: a soft X-ray component could only be detected so far in 5 dwarf novae in outburst and not in any nova-like variable. Also in high-accretion-rate systems there is a hot optically thin X-ray source, which has, however, an X-ray luminosity which is much less than the UV luminosity of the system (van Teeseling & Verbunt 1994). Finally, there is evidence for orbital modulation in the X-rays from some systems (e.g. van Teeseling et al. 1995).

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 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 The Characteristics of Magnetic CVs in the Period Gap

2004 ◽  
Vol 190 ◽  
pp. 15-21 ◽  
Author(s):  
Gaghik Tovmassian ◽  
Sergey Zharikov ◽  
Ronald Mennickent ◽  
Jochen Greiner
Keyword(s):  
Mass Transfer ◽  
Orbital Period ◽  
Accretion Rate ◽  
Cataclysmic Variables ◽  
Magnetic Systems ◽  
Transfer Rates ◽  
Significant Difference ◽  
Magnetic Cataclysmic Variables

AbstractWe have observed several magnetic cataclysmic variables located in the range between 2 and 3 hours, known as the period gap. This work was prompted by the recent discovery of RXJ1554.2+2721. It has 2.54 hours orbital period and shows almost pure cyclotron continuum in a low luminosity state, similar to HS1023+3900, HS0922+1333 and RBS206. These are low accretion rate polars (LARPs) known to have mass transfer rates of order of a few 10-13M⊙/year. The aim of the study was to find out, if magnetic systems filling the period gap are in any way different from their counterparts outside that range of periods. The only significant difference we encounter is a much higher number of asynchronous magnetic systems towards longer periods than below the gap.

scholarly journals The Effective Temperature Distribution Function of Cataclysmic Variable White Dwarfs

1987 ◽  
Vol 93 ◽  
pp. 47-51
Author(s):  
E.M. Sion
Keyword(s):  
Distribution Function ◽  
Temperature Distribution ◽  
Orbital Period ◽  
White Dwarf ◽  
White Dwarfs ◽  
Cataclysmic Variables ◽  
Cataclysmic Variable ◽  
Term Evolution ◽  
Effective Temperatures

AbstractWith the recent detection of direct white dwarf photospheric radiation from certain cataclysmic variables in quiescent (low accretion) states, important implications and clues about the nature and long-term evolution of cataclysmic variables can emerge from an analysis of their physical properties. Detection of the underlying white dwarfs has led to a preliminary empirical CV white dwarf temperature distribution function and, in a few cases, the first detailed look at a freshly accreted while dwarf photosphere. The effective temperatures of CV white dwarfs plotted versus orbital period for each type of CV appears to reveal a tendency for the cooler white dwarf primaries to reside in the shorter period systems. Possible implications are briefly discussed.

scholarly journals High Speed UV Photometry of the AM Her Systems AM Her, VV Pup And V834 Cen, with the Hubble Space Telescope

1996 ◽  
Vol 158 ◽  
pp. 223-224
Author(s):  
K. Schaefer ◽  
H. Bond ◽  
G. Chanmugam
Keyword(s):  
Preliminary Analysis ◽  
High Speed ◽  
Hubble Space Telescope ◽  
Cataclysmic Variables ◽  
Low Frequency ◽  
Gabor Transform ◽  
Periodic Oscillations ◽  
Space Telescope ◽  
Uv Photometry ◽  
Magnetic Cataclysmic Variables

We have used the High Speed Photometer (HSP) aboard the Hubble Space Telescope to observe the magnetic cataclysmic variables VV Pup, AM Her, and V834 Cen in the UV (1400…3300 Å) with 0.01 s time resolution. We detected low frequency flickering in all three systems, and compare the time-scales with the predictions of King (1989). At higher frequencies we searched for shock oscillations from the accretion column(s) in these systems. The data were analyzed using the Gabor transform wavelet-like technique (Heil & Walnut 1989) to search for frequency evolution throughout each observation. Preliminary analysis suggests the detection of rapid UV quasi-periodic oscillations (QPOs) in VV Pup at 0.74 Hz, and at 4.4 Hz in V834 Cen. As in ground based observations, our observations failed to yield any rapid QPOs in AM Her itself.

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