X-ray emission from massive stars with magnetic fields
L.M. Oskinova1, W.-R. Hamann1 J.P. Cassinelli2, J.C. Brown3, H. Todt1,
1 Institute for Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany
2 Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53711, USA
3 School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, UK
We investigate the connections between the magnetic fields and the X-ray
emission from massive stars. Our study shows
that the X-ray properties of known strongly magnetic stars are diverse:
while some comply to the predictions of the
magnetically confined wind model, others do not. We conclude that
strong, hard, and variable X-ray emission may be a
sufficient attribute of magnetic massive stars, but it is not a
necessary one. We address the general properties of X-ray
emission from "normal" massive stars, especially the long standing
mystery about the correlations between the parameters
of X-ray emission and fundamental stellar properties. The recent
development in stellar structure modeling shows that
small scale surface magnetic fields may be common. We suggest a "hybrid"
scenario which could explain the X-ray
emission from massive stars by a combination of magnetic mechanisms on
the surface and shocks in the stellar wind. The
magnetic mechanisms and the wind shocks are triggered by convective
motions in sub-photospheric layers. This scenario
opens the door for a natural explanation of the well established
correlation between bolometric and X-ray luminosities.
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