scholarly journals Wolf-Rayet Stellar Wind Theory

1991 ◽  
Vol 143 ◽  
pp. 289-308
Author(s):  
J. P. Cassinelli
Keyword(s):  
Magnetic Fields ◽  
Stellar Wind ◽  
Equatorial Zone ◽  
Radio Flux ◽  
Polar Wind ◽  
Radiative Processes ◽  
Rotator Model ◽  
Show Evidence ◽  
Wind Theory

Two possible solutions to the Wolf-Rayet wind momentum problem are discussed: purely radiation driven wind theory, with multi-line effects, and Luminous Magnetic Rotator theory. Several recently developed radiative processes for enhancing M or v∞ are described, and it is concluded that only the winds of rather hot luminous Wolf-Rayet stars could possibly be driven by radiation. These stars should show evidence of acceleration at large radial distances. For the rapid rotators, it is possible to drive a dense equatorial outflow. Limits are discussed regarding the needed surface magnetic fields. With this model, the wind momentum problem is solved in a piece-wise fashion by having the large radio flux of Wolf-Rayet stars come from the equatorial zone and the broad P Cygni lines, arising in the polar wind. The Luminous Magnetic Rotator model can also be tested through observation, primarily through spectropolarimetry.

scholarly journals On the influence of magnetic fields in neutral planetary wakes

2016 ◽  
Vol 12 (S328) ◽  
pp. 192-197
Author(s):  
C. Villarreal D’Angelo ◽  
M. Schneiter ◽  
A. Esquivel
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Radiation Pressure ◽  
Stellar Wind ◽  
Magnetic Moments ◽  
Radiative Processes ◽  
Planetary Magnetic Fields ◽  
Stellar Magnetic Fields

AbstractWe present a 3D magnetohydrodynamic study of the effect that stellar and planetary magnetic fields have on the calculated Lyα absorption during the planetary transit, employing parameters that resemble the exoplanet HD209458b. We assume a dipolar magnetic field for both the star and the planet, and use the Parker solution to initialize the stellar wind. We also consider the radiative processes and the radiation pressure.We use the numerical MHD code Guacho to run several models varying the values of the planetary and stellar magnetic moments within the range reported in the literature.We found that the presence of magnetic fields influences the escaping neutral planetary material spreading the absorption Lyα line for large stellar magnetic fields.

Peculiarity Parameters

1976 ◽  
Vol 32 ◽  
pp. 233-254
Author(s):  
H. M. Maitzen
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Theoretical Work ◽  
Observational Evidence ◽  
Rotator Model ◽  
Peculiar Behaviour ◽  
Field Spectrum ◽  
Oblique Rotator ◽  
Ap Stars ◽  
The Way

Ap stars are peculiar in many aspects. During this century astronomers have been trying to collect data about these and have found a confusing variety of peculiar behaviour even from star to star that Struve stated in 1942 that at least we know that these phenomena are not supernatural. A real push to start deeper theoretical work on Ap stars was given by an additional observational evidence, namely the discovery of magnetic fields on these stars by Babcock (1947). This originated the concept that magnetic fields are the cause for spectroscopic and photometric peculiarities. Great leaps for the astronomical mankind were the Oblique Rotator model by Stibbs (1950) and Deutsch (1954), which by the way provided mathematical tools for the later handling pulsar geometries, anti the discovery of phase coincidence of the extrema of magnetic field, spectrum and photometric variations (e.g. Jarzebowski, 1960).

scholarly journals Magnetic Braking and the Oblique Rotator Model

1970 ◽  
Vol 4 ◽  
pp. 269-273
Author(s):  
L. Mestel ◽  
C. S. Selley
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Stellar Wind ◽  
Rotation Axis ◽  
Dynamical Evolution ◽  
Magnetic Star ◽  
Rotator Model ◽  
Oblique Rotator ◽  
Magnetic Braking

This work investigates the dynamical evolution of a rotating magnetic star which drives a stellar wind. The basic magnetic field of the star is supposed symmetric about an axis, which is inclined at an angle X to the rotation axis k (Figure 1). We adopt the familiar equations of an inviscid perfectly conducting gas. In a steady state, the velocity as seen in a frame rotating with the star is taken as

scholarly journals The B[e] stars

1989 ◽  
Vol 113 ◽  
pp. 117-120
Author(s):  
F.-J. Zickgraf
Keyword(s):  
Physical Properties ◽  
Stellar Wind ◽  
Main Sequence ◽  
Massive Stars ◽  
High Mass ◽  
Sequence Evolution ◽  
Two Component ◽  
Show Evidence ◽  
High Mass Loss ◽  
General Appearance

AbstractB[e] supergiants show evidence for a non-spherical two-component stellar wind. The general appearance and the physical properties of the suggested disk-like configuration are discussed. The high mass-loss rates, the surprisingly large number and the location in the H-R diagram make these stars important for the understanding of the post-main-sequence evolution of massive stars.

scholarly journals DECREASING SUNSPOT MAGNETIC FIELDS EXPLAIN UNIQUE 10.7 cm RADIO FLUX

2012 ◽  
Vol 757 (1) ◽  
pp. L8 ◽  
Author(s):  
W. Livingston ◽  
M. J. Penn ◽  
L. Svalgaard
Keyword(s):  
Magnetic Fields ◽  
Radio Flux

Optical polarimetry of nebulae in regions of star formation

1986 ◽  
Vol 64 (4) ◽  
pp. 426-430 ◽  
Author(s):  
S. M. Scarrott ◽  
R. F. Warren-Smith ◽  
P. W. Draper ◽  
T. M. Gledhill
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Optical Polarization ◽  
Polarization Data ◽  
Dark Clouds ◽  
Show Evidence

Optical polarization data are presented for nebulosities associated with dark clouds and regions of star formation.Illuminating sources are identified, and it is found that these usually show evidence of polarization induced by aligned grains, which we believe indicates the presence of magnetic fields in the gas–dust tori that surround the central objects.

scholarly journals Stellar-wind theory for O and B stars

1970 ◽  
Vol 36 ◽  
pp. 236-237
Author(s):  
Philip M. Solomon
Keyword(s):  
Mass Loss ◽  
Radiation Pressure ◽  
Stellar Wind ◽  
Conclusive Evidence ◽  
Driving Mechanism ◽  
Gravitational Acceleration ◽  
Hot Stars ◽  
B Stars ◽  
Wind Theory ◽  
Ultraviolet Observations

The rocket-ultraviolet observations of strong Doppler-shifted absorption lines of Siiv, Civ, Nv and other ions in the spectrum of O and B supergiants clearly indicate a high velocity outflow of matter from these stars. The presence of moderate ionisation stages in the stellar wind is conclusive evidence that the flow cannot be due to a high temperature corona as is the case for the solar wind. It is shown that the driving mechanism for the hot-star mass loss is radiation pressure exerted on the gas through absorption in resonance lines occurring at wavelengths near the maximum of the star's continuum flux. In the upper layers of these stars the outward force per gram of matter due to the radiation pressure can greatly exceed the gravitational acceleration making a static atmosphere impossible.The problem of a steady-state moving reversing layer is formulated and the solution leads to predictions of mass-loss rates as a function of effective temperature and gravity for all hot stars. These results are in substantial agreement with the observations.

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