On the Statistics of AM Herculis Binaries

1995 ◽  
Vol 12 (2) ◽  
pp. 165-169 ◽  
Author(s):  
Kinwah Wu ◽  
Dayal T. Wickramasinghe ◽  
Jianke Li
Keyword(s):  
Magnetic Field ◽  
Orbital Period ◽  
High Field ◽  
White Dwarfs ◽  
Cataclysmic Variables ◽  
Cataclysmic Variable ◽  
The Difference ◽  
The Magnetic Field ◽  
Very High

AbstractThe magnetic field and orbital period distributions of AM Herculis binaries are investigated. Our study shows that (i) there is a significant lack of very-high-field magnetic white dwarfs in binaries when compared with isolated white dwarfs, and (ii) the difference between the period distributions of AM Herculis binaries and other cataclysmic variable subclasses is statistically significant. These results imply that the evolution and the birth of AM Herculis binaries are different from those of other cataclysmic variables.

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.

MAGNETO-OPTICAL ROTATION IN VERY HIGH FIELDS

1960 ◽  
Vol 38 (7) ◽  
pp. 941-944 ◽  
Author(s):  
Richard Stevenson
Keyword(s):  
Magnetic Field ◽  
High Field ◽  
Optical Rotation ◽  
Field Limit ◽  
Electron Theory ◽  
Important Data ◽  
Kerr Rotation ◽  
High Fields ◽  
The Magnetic Field ◽  
Very High

Magneto-optical rotation by transmission through or reflection from solids is examined by the classical free electron theory, with the view of taking such a measurement using fields in the megagauss range. In general the rotation is a markedly non-linear function of the magnetic field, and in some cases can change in sign as the field increases. For very low fields the rotation varies directly with B, but in the high field limit the rotation varies inversely with the field. For substances in which the intercollision time of the electron is small, measurements of the Kerr rotation (i.e. by reflection) will give the electron mobility as a function of the magnetic field, and thus will give important data which can be used in conjunction with high field magnetoresistance experiments.

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 Discovery of a young pre-intermediate polar

2021 ◽  
Author(s):  
David J Wilson ◽  
Odette Toloza ◽  
John D Landstreet ◽  
Boris T Gänsicke ◽  
Jeremy J Drake ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
White Dwarf ◽  
White Dwarfs ◽  
Hubble Space Telescope ◽  
Cataclysmic Variables ◽  
Rotation Period ◽  
Field Measurements ◽  
The Magnetic Field

Abstract We present the discovery of a magnetic field on the white dwarf component in the detached post common envelope binary (PCEB) CC Cet. Magnetic white dwarfs in detached PCEBs are extremely rare, in contrast to the high incidence of magnetism in single white dwarfs and cataclysmic variables. We find Zeeman-split absorption lines in both ultraviolet Hubble Space Telescope (HST) spectra and archival optical spectra of CC Cet. Model fits to the lines return a mean magnetic field strength of 〈|B|〉 ≈ 600–700 kG. Differences in the best-fit magnetic field strength between two separate HST observations and the high v sin  i of the lines indicate that the white dwarf is rotating with a period ∼0.5 hours, and that the magnetic field is not axisymmetric about the spin axis. The magnetic field strength and rotation period are consistent with those observed among the intermediate polar class of cataclysmic variable, and we compute stellar evolution models that predict CC Cet will evolve into an intermediate polar in 7–17 Gyr. Among the small number of known PCEBs containing a confirmed magnetic white dwarf, CC Cet is the hottest (and thus youngest), with the weakest field strength, and cannot have formed via the recently proposed crystallisation/spin-up scenario. In addition to the magnetic field measurements, we update the atmospheric parameters of the CC Cet white dwarf via model spectra fits to the HST data and provide a refined orbital period and ephemeris from TESS photometry.

scholarly journals Magnetic Field Topology of Accreting White Dwarfs

2004 ◽  
Vol 190 ◽  
pp. 71-77 ◽  
Author(s):  
Klaus Reinsch ◽  
Fabian Euchner ◽  
Klaus Beuermann ◽  
Stefan Jordan
Keyword(s):  
Magnetic Field ◽  
White Dwarfs ◽  
Cataclysmic Variables ◽  
Systematic Investigation ◽  
Magnetic Field Topology ◽  
First Results ◽  
Global Magnetic Field ◽  
Magnetic Cataclysmic Variables ◽  
Polarization Spectra ◽  
The Magnetic Field

AbstractWe report first results of our systematic investigation of the magnetic field structure of rotating single magnetic white dwarfs and of white dwarfs in magnetic cataclysmic variables. The global magnetic field distributions on the isolated white dwarf HE 1045-0908 and the accreting white dwarfs in EF Eri and CP Tuc have been derived from phase-resolved flux and polarization spectra obtained with FORS1 at the ESO VLT using the systematic method of Zeeman tomography.

scholarly journals The Period and Magnetic Field Distributions of Cataclysmic Variables: Implications for their Evolution

1987 ◽  
Vol 93 ◽  
pp. 549-555
Author(s):  
G.D. Schmidt ◽  
J. Liebert
Keyword(s):  
Magnetic Field ◽  
White Dwarfs ◽  
Cataclysmic Variables ◽  
Selection Effects ◽  
Magnetic Systems ◽  
Field Distributions ◽  
Short Period ◽  
Order Of Magnitude ◽  
Orbital Periods ◽  
The Magnetic Field

AbstractComparison of the period distributions of various classes of CVs confirms an extreme bias of the synchronous AM Her systems toward short orbital periods, while the DQ Her systems do not differ significantly from the distribution of non-magnetic systems. This suggests either strong selection effects or enhanced evolution of the AM Her systems. There is as yet no obvious bimodality in either the magnetic field distributions of isolated white dwarfs or of CV primaries. However, clear differences between the two exist: the strongest being that magnetic primaries are overrepresented among short period CVs by more than an order of magnitude in comparison to the field white dwarfs.

scholarly journals First in-orbit results of the vector magnetic field measurement of the High Precision Magnetometer onboard the China Seismo-Electromagnetic Satellite

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Bin Zhou ◽  
Bingjun Cheng ◽  
Xiaochen Gou ◽  
Lei Li ◽  
Yiteng Zhang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Precision ◽  
Magnetic Field Measurement ◽  
Vector Data ◽  
Magnetic Field Data ◽  
Night Side ◽  
The Difference ◽  
The Magnetic Field ◽  
Ground Calibration ◽  
Data Calibration

Abstract The High Precision Magnetometer (HPM) is one of the main payloads onboard the China Seismo-Electromagnetic Satellite (CSES). The HPM consists of two Fluxgate Magnetometers (FGM) and the Coupled Dark State Magnetometer (CDSM), and measures the magnetic field from DC to 15 Hz. The FGMs measure the vector components of the magnetic field; while the CDSM detects the magnitude of the magnetic field with higher accuracy, which can be used to calibrate the linear parameters of the FGM. In this paper, brief descriptions of measurement principles and performances of the HPM, ground, and in-orbit calibration results of the FGMs are presented, including the thermal drift and magnetic interferences from the satellite. The HPM in-orbit vector data calibration includes two steps: sensor non-linearity corrections based on on-ground calibration and fluxgate linear parameter calibration based on the CDSM measurements. The calibration results show a reasonably good stability of the linear parameters over time. The difference between the field magnitude calculated from the calibrated FGM components and the magnitude directly measured by the CDSM is just 0.5 nT (1σ) when the linear parameters are fitted separately for the day- and the night-side. Satellite disturbances have been analyzed including soft and hard remanence as well as magnetization of the magnetic torquer, radiation from the Tri-Band Beacon, and interferences from the rotation of the solar wing. A comparison shows consistency between the HPM and SWARM magnetic field data. Observation examples are introduced in the paper, which show that HPM data can be used to survey the global geomagnetic field and monitor the magnetic field disturbances in the ionosphere.

The Magnetic Anisotropy of Stretched Rubber as a Function of the Tension to Which It Is Subjected

1945 ◽  
Vol 18 (1) ◽  
pp. 8-9 ◽  
Author(s):  
Eugénie Cotton-Feytis
Keyword(s):  
Magnetic Field ◽  
Magnetic Anisotropy ◽  
Uniaxial Crystal ◽  
Horizontal Magnetic Field ◽  
First Approximation ◽  
The Difference ◽  
The Times ◽  
Angular Displacements ◽  
The Magnetic Field ◽  
Oscillation Method

Abstract From the standpoint of its magnetic anisotropy, stretched rubber is comparable in a first approximation to a uniaxial crystal, in which the direction of the axis is the same as the direction of elongation. It is possible to measure this anisotropy by means of the oscillation method used by Krishnan, Guha and Banerjee in studying crystals. The sample to be examined is suspended in a uniform horizontal magnetic field in such a manner that its axis is horizontal. It is then so arranged that the torsion of the suspension wire is zero when the rubber sample is in a position of equilibrium in the field. The times of oscillation T′ and T for very small angular displacements around this position, in the presence and then in the absence of the magnetic field, are then recorded. In this way the difference between the specific susceptibilities in the direction of the axis and in the horizontal direction perpendicular to the axis is calculated by application of the equation:

Effect of a static magnetic field onEscherichia coliadhesion and orientation

2016 ◽  
Vol 62 (11) ◽  
pp. 944-952 ◽  
Author(s):  
Lotfi Mhamdi ◽  
Nejib Mhamdi ◽  
Naceur Mhamdi ◽  
Philippe Lejeune ◽  
Nicole Jaffrezic ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Bacterial Adhesion ◽  
Parallel Magnetic Field ◽  
Field Orientation ◽  
Static Magnetic Fields ◽  
Preliminary Study ◽  
The Difference ◽  
The Magnetic Field

This preliminary study focused on the effect of exposure to 0.5 T static magnetic fields on Escherichia coli adhesion and orientation. We investigated the difference in bacterial adhesion on the surface of glass and indium tin oxide-coated glass when exposed to a magnetic field either perpendicular or parallel to the adhesion surface (vectors of magnetic induction are perpendicular or parallel to the adhesion surface, respectively). Control cultures were simultaneously grown under identical conditions but without exposure to the magnetic field. We observed a decrease in cell adhesion after exposure to the magnetic field. Orientation of bacteria cells was affected after exposure to a parallel magnetic field. On the other hand, no effect on the orientation of bacteria cells was observed after exposure to a perpendicular magnetic field.

High magnetic field NMR investigation of the spin density wave phase of TMTSF2PF6

2002 ◽  
Vol 12 (9) ◽  
pp. 389-389
Author(s):  
W. G. Clark ◽  
F. Zamborsky ◽  
B. Alavi ◽  
P. Vonlanthen ◽  
W. Moulton ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Spin Density ◽  
Density Wave ◽  
Spin Density Wave ◽  
Proton Relaxation ◽  
High Magnetic Fields ◽  
Organic Conductor ◽  
First Order ◽  
The Magnetic Field ◽  
Very High

We report proton NMR measurements of the effect of very high magnetic fields up to 44.7 T (1.9 GHz) on the spin density wave (SDW) transition of the organic conductor TMTSF2PF6. Up to 1.8 GHz, no effect of critical slowing close to the transition is seen on the proton relaxation rate (1/T1), which is determined by the SDW fluctuations associated with the phase transition at the NMR frequency. Thus, the correlation time for such fluctuations is less than $1O^{-10}$s. A possible explanation for the absence of longer correlation times is that the transition is weakly first order, so that the full critical divergence is never achieved. The measurements also show a dependence of the transition temperature on the orientation of the magnetic field and a quadratic dependence on its magnitude that agrees with earlier transport measurements at lower fields. The UCLA part of this work was supported by NSF Grant DMR-0072524.

Sign in / Sign up

Export Citation Format

Share Document