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X-rays from magnetic massive OB stars

Published online by Cambridge University Press:  07 August 2014

V. Petit ,
D. H. Cohen ,
Y. Nazé ,
M. Gagné ,
R. H. D. Townsend ,
M. A. Leutenegger ,
A. ud-Doula ,
S. P. Owocki  and
G. A. Wade
V. Petit
Affiliation:
Dept. of Physics & Astronomy, University of Delaware, Newark, DE, USA email: [email protected]
D. H. Cohen
Affiliation:
Dept. of Physics & Astronomy, Swarthmore College, Swarthmore, PA, USA
Y. Nazé
Affiliation:
GAPHE Dépt. AGO, Université de Liège, Liège, Belgium
M. Gagné
Affiliation:
Dept. of Geology & Astronomy, West Chester University, West Chester, PA, USA
R. H. D. Townsend
Affiliation:
Dept. of Astronomy, University of Wisconsin-Madison, Madison, WI, USA
M. A. Leutenegger
Affiliation:
Laboratory for High Energy Astrophysics, NASA/GSFC, Greenbelt, MD, USA
A. ud-Doula
Affiliation:
Penn State Worthington Scranton, Dunmore, PA, USA
S. P. Owocki
Affiliation:
Dept. of Physics & Astronomy, University of Delaware, Newark, DE, USA email: [email protected]
G. A. Wade
Affiliation:
Dept. of Physics, Royal Military College of Canada, Kingston, ON, Canada
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Abstract

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The magnetic activity of solar-type and low-mass stars is a well known source of coronal X-ray emission. At the other end of the main sequence, X-rays emission is instead associated with the powerful, radiatively driven winds of massive stars. Indeed, the intrinsically unstable line-driving mechanism of OB star winds gives rise to shock-heated, soft emission (~0.5 keV) distributed throughout the wind. Recently, the latest generation of spectropolarimetric instrumentation has uncovered a population of massive OB-stars hosting strong, organized magnetic fields. The magnetic characteristics of these stars are similar to the apparently fossil magnetic fields of the chemically peculiar ApBp stars. Magnetic channeling of these OB stars' strong winds leads to the formation of large-scale shock-heated magnetospheres, which can modify UV resonance lines, create complex distributions of cooled Halpha emitting material, and radiate hard (~2-5 keV) X-rays. This presentation summarizes our coordinated observational and modelling efforts to characterize the manifestation of these magnetospheres in the X-ray domain, providing an important contrast between the emission originating in shocks associated with the large-scale fossil fields of massive stars, and the X-rays associated with the activity of complex, dynamo-generated fields in lower-mass stars.

Keywords

Stars – early-typeStars – magnetic fields
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 9 , Symposium S302: Magnetic Fields throughout Stellar Evolution , August 2013 , pp. 330 - 333
Copyright
Copyright © International Astronomical Union 2014 

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