Connection between nonradial pulsations and stellar winds in massive stars. VI - Variability in H alpha, polarization, and magnetic fields in early-type stars

1986 ◽  
Vol 98 ◽  
pp. 44 ◽  
Author(s):  
P. Barker
Keyword(s):  
Magnetic Fields ◽  
Massive Stars ◽  
Stellar Winds ◽  
Early Type ◽  
Early Type Stars

scholarly journals X-ray diagnostics of massive star winds

2016 ◽  
Vol 12 (S329) ◽  
pp. 151-155
Author(s):  
L. M. Oskinova ◽  
R. Ignace ◽  
D. P. Huenemoerder
Keyword(s):  
High Resolution ◽  
Stellar Wind ◽  
Massive Star ◽  
Massive Stars ◽  
Stellar Winds ◽  
X Rays ◽  
Early Type ◽  
Stellar Rotation ◽  
X Ray ◽  
Early Type Stars

AbstractObservations with powerful X-ray telescopes, such as XMM-Newton and Chandra, significantly advance our understanding of massive stars. Nearly all early-type stars are X-ray sources. Studies of their X-ray emission provide important diagnostics of stellar winds. High-resolution X-ray spectra of O-type stars are well explained when stellar wind clumping is taking into account, providing further support to a modern picture of stellar winds as non-stationary, inhomogeneous outflows. X-ray variability is detected from such winds, on time scales likely associated with stellar rotation. High-resolution X-ray spectroscopy indicates that the winds of late O-type stars are predominantly in a hot phase. Consequently, X-rays provide the best observational window to study these winds. X-ray spectroscopy of evolved, Wolf-Rayet type, stars allows to probe their powerful metal enhanced winds, while the mechanisms responsible for the X-ray emission of these stars are not yet understood.

scholarly journals Stellar Winds from Massive Stars: The Influence of X-Rays on the Dynamics

1991 ◽  
Vol 143 ◽  
pp. 318-318
Author(s):  
I. Stevens ◽  
G. Cooper ◽  
S. Owocki
Keyword(s):  
Theoretical Investigation ◽  
Massive Stars ◽  
Stellar Winds ◽  
X Rays ◽  
Early Type ◽  
Early Type Stars

We report on a theoretical investigation of the X-rays observed from early type stars on the global wind dynamics.

scholarly journals The B Fields in OB Stars (BOB) Survey

2014 ◽  
Vol 9 (S307) ◽  
pp. 342-347 ◽  
Author(s):  
T. Morel ◽  
N. Castro ◽  
L. Fossati ◽  
S. Hubrig ◽  
N. Langer ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Lower Bound ◽  
Magnetic Fields ◽  
Field Strength ◽  
Massive Stars ◽  
Occurrence Rate ◽  
Early Type ◽  
Ob Stars ◽  
Early Type Stars ◽  
Field Formation

AbstractThe B fields in OB stars (BOB) survey is an ESO large programme collecting spectropolarimetric observations for a large number of early-type stars in order to study the occurrence rate, properties, and ultimately the origin of magnetic fields in massive stars. As of July 2014, a total of 98 objects were observed over 20 nights with FORS2 and HARPSpol. Our preliminary results indicate that the fraction of magnetic OB stars with an organised, detectable field is low. This conclusion, now independently reached by two different surveys, has profound implications for any theoretical model attempting to explain the field formation in these objects. We discuss in this contribution some important issues addressed by our observations (e.g., the lower bound of the field strength) and the discovery of some remarkable objects.

scholarly journals The Metallicity Dependence of the Mass Loss of Early-Type Massive Stars

2007 ◽  
Vol 3 (S250) ◽  
pp. 39-46
Author(s):  
Alex de Koter
Keyword(s):  
Mass Loss ◽  
Metal Content ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
Stellar Winds ◽  
Early Type ◽  
The Galaxy ◽  
Early Type Stars ◽  
Good Agreement ◽  
Comprehensive Study

AbstractWe report on a comprehensive study of the wind properties of 115 O- and early B-type stars in the Galaxy and the Large Magellanic Clouds. This work is part of the VLT/FLAMES Survey of Massive Stars. The data is used to construct the empirical dependence of the mass-loss in stellar winds on the metal content of their atmospheres. The metal content of early-type stars in the Magellanic Clouds is discussed. Assuming a power-law dependence of mass loss on metal content, Ṁ ∝ Zm, we find m = 0.83 ± 0.16 from an analysis of the wind momentum luminosity relation (Mokiem et al. 2007b). This result is in good agreement with the prediction m = 0.69 ± 0.10 by Vink et al. (2001). Though the scaling agrees, the absolute empirical value of mass loss is found to be a factor of two higher than predictions. This may be explained by a modest amount of clumping in the outflows of the objects studied.

scholarly journals Impact of rotation on the geometrical configurations of fossil magnetic fields

2014 ◽  
Vol 9 (S307) ◽  
pp. 373-374
Author(s):  
C. Emeriau ◽  
S. Mathis
Keyword(s):  
Magnetic Fields ◽  
Stellar Evolution ◽  
Large Scale ◽  
Massive Stars ◽  
Stellar Mass ◽  
Equilibrium States ◽  
Early Type ◽  
Mhd Equilibrium ◽  
Early Type Stars ◽  
Theoretical Results

AbstractThe MiMeS project demonstrated that a small fraction of massive stars (around 7%) presents large-scale, stable, generally dipolar magnetic fields at their surface. These fields that do not present any evident correlations with stellar mass or rotation are supposed to be fossil remnants of the initial phases of stellar evolution. They result from the relaxation to MHD equilibrium states, during the formation of stable radiation zones, of initial fields resulting from a previous convective phase. In this work, we present new theoretical results, where we generalize previous studies by taking rotation into account. The properties of relaxed fossil fields are compared to those obtained when rotation is ignored. Consequences for magnetic fields in the radiative envelope of rotating early-type stars and their stability are finally discussed.

scholarly journals The nature and origin of magnetic fields in early-type stars

2013 ◽  
Vol 9 (S302) ◽  
pp. 255-264 ◽  
Author(s):  
Jonathan Braithwaite
Keyword(s):  
Field Theory ◽  
Magnetic Fields ◽  
Massive Stars ◽  
Current Knowledge ◽  
Magnetic Activity ◽  
Early Type ◽  
Strong Magnetic Fields ◽  
Early Type Stars

AbstractI review our current knowledge of magnetic fields in stars more massive than around 1.5 M⊙, in particular their nature and origin. This includes the strong magnetic fields found in a subset of the population and the fossil field theory invoked to explain them; the subgauss fields detected in Vega and Sirius and their possible origin; and what we can infer about magnetic activity in massive stars and how it might be linked to subsurface convection.

scholarly journals The properties of early-type stars in the Magellanic Clouds

2008 ◽  
Vol 4 (S256) ◽  
pp. 325-336
Author(s):  
Christopher J. Evans
Keyword(s):  
Physical Properties ◽  
Mass Loss ◽  
Temperature Scale ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
Early Type ◽  
The Past ◽  
The Galaxy ◽  
Stellar Temperature ◽  
Early Type Stars

AbstractThe past decade has witnessed impressive progress in our understanding of the physical properties of massive stars in the Magellanic Clouds, and how they compare to their cousins in the Galaxy. I summarise new results in this field, including evidence for reduced mass-loss rates and faster stellar rotational velocities in the Clouds, and their present-day compositions. I also discuss the stellar temperature scale, emphasizing its dependence on metallicity across the entire upper-part of the Hertzsprung-Russell diagram.

scholarly journals The VLT-FLAMES survey of massive stars: mass loss and rotation of early-type stars in the SMC

2006 ◽  
Vol 456 (3) ◽  
pp. 1131-1151 ◽  
Author(s):  
M. R. Mokiem ◽  
A. de Koter ◽  
C. J. Evans ◽  
J. Puls ◽  
S. J. Smartt ◽  
...  
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Early Type ◽  
Early Type Stars

scholarly journals Massive stars: stellar models and stellar yields, impact on Galactic Archaeology

2017 ◽  
Vol 13 (S334) ◽  
pp. 170-177
Author(s):  
Georges Meynet ◽  
Arthur Choplin ◽  
Sylvia Ekström ◽  
Cyril Georgy
Keyword(s):  
Magnetic Fields ◽  
Mass Loss ◽  
Massive Stars ◽  
Stellar Winds ◽  
Stellar Models ◽  
The Impact

AbstractThe physics of massive stars depends (at least) on convection, mass loss by stellar winds, rotation, magnetic fields and multiplicity. We briefly discuss the impact of the first three processes on the stellar yields trying to identify some guidelines for future works.

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