scholarly journals Hot Magnetic Stars in Exotic Multiple Systems

2020 ◽  
Vol 240 ◽  
pp. 05003
Author(s):  
Eugene Semenko
Keyword(s):  
Magnetic Field ◽  
Binary Stars ◽  
The Other ◽  
Multiple Systems ◽  
Chemically Peculiar ◽  
Recent Advances ◽  
Magnetic Stars ◽  
Dynamo Mechanism ◽  
The Magnetic Field

A strong and stable magnetic field covering the whole surface is a landmark of chemically peculiar or CP stars. To explain the origin of mag- netic stars, several hypotheses were proposed, which depending on the mech- anism and time of formation can be grouped into three main. The magnetic field may originate in the protostellar medium (“fossil field”), turbulent layers of a star (“dynamo” mechanism) or in the other environment. In either scenario, binary stars appear as a merit of its reliability. Recent advances in observational astrophysics uncovered a bunch of new binary magnetic stars that were considered as rare before. We outline the results of studies of exotic binary and multiple systems with magnetic CP components: HD 6757, HD 34736, and HD 40759.

scholarly journals First magnetic stars

2008 ◽  
Vol 4 (S259) ◽  
pp. 399-400
Author(s):  
Iosif I. Romanyuk ◽  
Dimitry O. Kudryavtsev
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Field Strength ◽  
Main Sequence ◽  
Published Data ◽  
Rotating Stars ◽  
Exponential Law ◽  
Chemically Peculiar ◽  
Magnetic Stars ◽  
The Magnetic Field

AbstractThis contribution dedicated to the analysis of the magnetism of chemically peculiar (CP) stars of the upper Main Sequence. We use our own measurements and published data to compile a catalog of magnetic CP stars containing a total of 326 objects with confidently detected magnetic fields and 29 stars which are very likely to possess magnetic field. Our analysis shows that the number of magnetic CP stars decreases with increasing field strength in accordance with exponential law, hotter and faster rotating stars have stronger fields. Intensity of depressions in the continua correlates with the magnetic field strength.

scholarly journals The Magnetic Field and other Parameters of the Chemically Peculiar Stars

1986 ◽  
Vol 90 ◽  
pp. 33-36
Author(s):  
Glagolevskij Yu.V. ◽  
Romanyuk I.I. ◽  
Chunakova N.M.
Keyword(s):  
Magnetic Field ◽  
Surface Field ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Magnetic Stars ◽  
Chemically Peculiar Stars ◽  
Working Out ◽  
The Magnetic Field ◽  
Multicolor Photometry

The surface field Bs ( but not the effective Be one ) is responsible for different processes occuring in the magnetic stars atmospheres. For this reason it is natural that different investigators are interested in working out and improving methods of determination of Bs. Especially great attention attracts the method based on using the multicolor Geneva photometry. Cramer and Maeder have found a dependence between Bs and parameter Z of multicolor photometry wich they use for the estimation of the surface field. But it is necessary to investigate this method before application. Due to this reason we have put the following two problems:A - The search for stars with a maximal predicted fieldB - Examination of calibration of Bs (Z).

scholarly journals THE ENERGY EIGENVALUES OF THE TWO DIMENSIONAL HYDROGEN ATOM IN A MAGNETIC FIELD

2006 ◽  
Vol 15 (06) ◽  
pp. 1263-1271 ◽  
Author(s):  
A. SOYLU ◽  
O. BAYRAK ◽  
I. BOZTOSUN
Keyword(s):  
Magnetic Field ◽  
Hydrogen Atom ◽  
Iteration Method ◽  
Weak Magnetic Field ◽  
The Other ◽  
Asymptotic Iteration Method ◽  
Iterative Approach ◽  
Two Dimensional ◽  
Energy Eigenvalues ◽  
The Magnetic Field

In this paper, the energy eigenvalues of the two dimensional hydrogen atom are presented for the arbitrary Larmor frequencies by using the asymptotic iteration method. We first show the energy eigenvalues for the case with no magnetic field analytically, and then we obtain the energy eigenvalues for the strong and weak magnetic field cases within an iterative approach for n=2-10 and m=0-1 states for several different arbitrary Larmor frequencies. The effect of the magnetic field on the energy eigenvalues is determined precisely. The results are in excellent agreement with the findings of the other methods and our method works for the cases where the others fail.

scholarly journals The influence of resistivity gradients on shock conditions for a Petschek reconnection geometry

2016 ◽  
Vol 34 (4) ◽  
pp. 421-425
Author(s):  
Christian Nabert ◽  
Karl-Heinz Glassmeier
Keyword(s):  
Magnetic Field ◽  
Necessary Conditions ◽  
The Other ◽  
Diffusion Region ◽  
Two Dimensional ◽  
Characteristic Velocity ◽  
Magnetohydrodynamic Equations ◽  
One Dimensional ◽  
The Magnetic Field ◽  
Alfven Velocity

Abstract. Shock waves can strongly influence magnetic reconnection as seen by the slow shocks attached to the diffusion region in Petschek reconnection. We derive necessary conditions for such shocks in a nonuniform resistive magnetohydrodynamic plasma and discuss them with respect to the slow shocks in Petschek reconnection. Expressions for the spatial variation of the velocity and the magnetic field are derived by rearranging terms of the resistive magnetohydrodynamic equations without solving them. These expressions contain removable singularities if the flow velocity of the plasma equals a certain characteristic velocity depending on the other flow quantities. Such a singularity can be related to the strong spatial variations across a shock. In contrast to the analysis of Rankine–Hugoniot relations, the investigation of these singularities allows us to take the finite resistivity into account. Starting from considering perpendicular shocks in a simplified one-dimensional geometry to introduce the approach, shock conditions for a more general two-dimensional situation are derived. Then the latter relations are limited to an incompressible plasma to consider the subcritical slow shocks of Petschek reconnection. A gradient of the resistivity significantly modifies the characteristic velocity of wave propagation. The corresponding relations show that a gradient of the resistivity can lower the characteristic Alfvén velocity to an effective Alfvén velocity. This can strongly impact the conditions for shocks in a Petschek reconnection geometry.

scholarly journals Dynamical Galactic Halos

1993 ◽  
Vol 157 ◽  
pp. 415-419
Author(s):  
D. Breitschwerdt ◽  
H.J. Völk ◽  
V. Ptuskin ◽  
V. Zirakashvili
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
The Other ◽  
Galactic Rotation ◽  
Galactic Halos ◽  
Magnetic Forces ◽  
Dynamical Coupling ◽  
Field Lines ◽  
The Magnetic Field ◽  
Open Magnetic Field

It is argued that the description of the magnetic field in halos of galaxies should take into account its dynamical coupling to the other major components of the interstellar medium, namely thermal plasma and cosmic rays (CR's). It is then inevitable to have some loss of gas and CR's (galactic wind) provided that there exist some “open” magnetic field lines, facilitating their escape, and a sufficient level of self-generated waves which couple the particles to the gas. We discuss qualitatively the topology of the magnetic field in the halo and show how galactic rotation and magnetic forces can be included in such an outflow picture.

scholarly journals Period spacings of gravity modes in rapidly rotating magnetic stars

2020 ◽  
Vol 636 ◽  
pp. A100 ◽  
Author(s):  
V. Prat ◽  
S. Mathis ◽  
C. Neiner ◽  
J. Van Beeck ◽  
D. M. Bowman ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Rotation Axis ◽  
Equatorial Region ◽  
Rotating Stars ◽  
Frequency Shifts ◽  
New Formalism ◽  
Magnetic Stars ◽  
Internal Oblique ◽  
Rapidly Rotating Stars ◽  
The Magnetic Field

Context. Stellar internal magnetic fields have recently been shown to leave a detectable signature on period spacing patterns of gravity modes. Aims. We aim to investigate the effect of the obliquity of a mixed (poloidal and toroidal) dipolar internal fossil magnetic field with respect to the rotation axis on the frequency of gravity modes in rapidly rotating stars. Methods. We used the traditional approximation of rotation to compute non-magnetic modes, and a perturbative treatment of the magnetic field to compute the corresponding frequency shifts. We applied the new formalism to HD 43317, a magnetic, rapidly rotating, slowly pulsating B-type star, whose field has an obliquity angle of about 80°. Results. We find that frequency shifts induced by the magnetic field on high-radial-order gravity modes are larger with increasing obliquity angle, when the magnetic axis is closer to the equatorial region, where these modes are trapped. The maximum value is reached for an obliquity angle of 90°. This trend is observed for all mode geometries. Conclusions. Our results predict that the signature of an internal oblique dipolar magnetic field is detectable using asteroseismology of gravity modes.

Schwingung eines Plasmazylinders in einem axialen Magnetfeld II

1960 ◽  
Vol 15 (3) ◽  
pp. 220-226 ◽  
Author(s):  
Klaus Körper
Keyword(s):  
Magnetic Field ◽  
Refractive Index ◽  
External Magnetic Field ◽  
Field Strength ◽  
Axial Magnetic Field ◽  
Surface Current ◽  
The Other ◽  
Plasma Cylinder ◽  
Resonance Frequencies ◽  
The Magnetic Field

Radial oscillations are excited in a homogeneous infinite plasma cylinder in a homogeneous axial magnetic field by a surface current which is homogeneous in the axial and azimuthal directions. The modes of oscillations corresponding to the axial and azimuthal components of current are not coupled, and so they may be analysed separately. The magnetic field in the plasma and vacuum is obtained, and the indices of refraction for both types of oscillations are discussed thoroughly. When the currents are parallel to the external magnetic field, the oscillations are characterized by the refractive index of Eccles. On the other hand, when the current is perpendicular to the magnetic field two resonance frequencies exist, which depend on the density of the plasma and the magnetic field strength. — In the latter case the radial characteristic oscillations of the plasma cylinder in an external magnetic field are considered.

Die Wirkung eines homogenen Magnetfeldes auf das Wachstum von Micrococcus denitrificans / The Influence of Homogeneous Magnetic Fields on the Growth of Micrococcus denitrificans

1970 ◽  
Vol 25 (9) ◽  
pp. 1020-1023 ◽  
Author(s):  
Wolfram Thiemann ◽  
Erich Wagner
Keyword(s):  
Magnetic Field ◽  
Saccharomyces Cerevisiae ◽  
Growth Rate ◽  
Magnetic Fields ◽  
The Other ◽  
Anaerobic Conditions ◽  
Inhibition Of Growth ◽  
Significant Acceleration ◽  
In The Beginning ◽  
The Magnetic Field

The influence of strong homogeneous magnetic fields in the range of 5000 to 8000 Gauss on the growth of Saccharomyces cerevisiae and Micrococcus denitrificans was studied. In the case of yeast growing under nearly anaerobic conditions an inhibition of growth rate was observed in the beginning of incubaton while some hours later the growth accelerated and surpassed the control. M. denitrificans on the other hand grew with the same rate as the controls during the first 2 - 3 hours of experiment; thereafter the magnetic field resulted in a significant acceleration of growth rate measured by a 5.8 to 13.3% increase of oxygen consumption after 5 - 6 hours run of experiment. Until now only inhibition of bacterial growths by magnetic fields is reported elsewhere in the literature.

Relation between wave speeds in the crust of dense magnetic stars

1978 ◽  
Vol 364 (1719) ◽  
pp. 537-552 ◽  
Keyword(s):  
Magnetic Field ◽  
Initial Pressure ◽  
The Body ◽  
Perfect Conductor ◽  
Initial State ◽  
Wave Speeds ◽  
Magnetic Stars ◽  
Arbitrary Strength ◽  
The Magnetic Field ◽  
Relativistic Framework

By studying, within the relativistic framework, the propagation of so-called infinitesimal discontinuities throughout a magnetized elastic perfect conductor in an initial state of high hydrostatic pressure p 0 and in the presence of a magnetic field of arbitrary strength, it is proven that there hold universal relations (i. e., that do not depend on the exact equation of state of the body) between the speeds U f and U s of so-called fast and slow magnetoelastic modes. These results, which should hold true in the crust of dense magnetic stars, have the following form. If A 0 is the relativistic Alfvén number of the initial state and a 0 is the sound speed of a fictitious relativistic perfect fluid whose law of compression would yield the initial pressure p o , then (with nondimensional speeds) U 2 / f = 4/3[ U 2 s (1+ A 2 0 ]+( a 2 0 -4/3 A 2 0 ) for a propagation along the magnetic field and U 2 f (1+ A 2 0 )=4/3 U 2 s +( a 2 0 + A 2 0 ) for a propagation in a direction orthogonal to the magnetic field. These results generalize previous results obtained in relativistic elasticity by Carter and Maugin.

Stability of static current sheets connecting plane magnetic null points

1999 ◽  
Vol 61 (4) ◽  
pp. 623-631
Author(s):  
MANUEL NÚÑEZ
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Lorentz Force ◽  
Critical Points ◽  
Null Point ◽  
The Other ◽  
Magnetic Null ◽  
Local Topology ◽  
The Magnetic Field ◽  
A Current

The configuration created in the plane by the separation of a magnetic hyperbolic null point into two critical points connected by a current sheet is considered. The main parameters are the orders of the zeros of these new null points, which determine the local topology of the magnetic field. It is shown that when the magnetic field is static, the fluid tends to flow orthogonally to the field in the vicinity of the sheet endpoints. Moreover, the Lorentz force pushes one of them towards the other, so the configuration tends to collapse again into a single null point except when the order of both is precisely ½.

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