• DOI:10.1093/mnras/sts344
• Corpus ID: 14961579

A magnetic confinement versus rotation classification of massive-star magnetospheres

@article{Petit2013AMC,
  title={A magnetic confinement versus rotation classification of massive-star magnetospheres},
  author={V{\'e}ronique Petit and Stanley P. Owocki and Gregg A. Wade and David H. Cohen and J. O. Sundqvist and M. Gagn'e and Jes'us Ma'iz Apell'aniz and Mary E. Oksala and David Bohlender and Th. Rivinius and Huib F. Henrichs and Evelyne Alecian and Richard H. D. Townsend and Asif ud-Doula and The MiMeS Collaboration},
  journal={Monthly Notices of the Royal Astronomical Society},
  year={2013},
  volume={429},
  pages={398-422}
}

• V. Petit, S. Owocki, +12 authors The MiMeS Collaboration
• Published 1 November 2012
• Physics
• Monthly Notices of the Royal Astronomical Society

Building on results from the Magnetism in Massive Stars (MiMeS) project, this paper shows how a two-parameter classification of massive-star magnetospheres in terms of the magnetic wind confinement (which sets the Alfv´ en radius RA) and stellar rotation (which sets the Kepler co-rotation radius RK) provides a useful organization of both observational signatures and theoretical predictions. We compile the first comprehensive study of inferred and observed values for relevant stellar and magnetic parameters of 64 confirmed magnetic OB stars with Teff 16 kK. Using these parameters, we locate the stars in the magnetic confinement–rotation diagram, a log–log plot of RK versus RA. This diagram can be subdivided into regimes of centrifugal magnetospheres (CM), with RA > RK ,v ersusdynamical magnetospheres (DM), with RK > RA. We show how key observational diagnostics, like the presence and characteristics of Hα emission, depend on a star’s position within the diagram, as well as other parameters, especially the expected wind mass-loss rates. In particular, we identify two distinct populations of magnetic stars with Hα emission: namely, slowly rotating O-type stars with narrow emission consistent with a DM, and more rapidly rotating B-type stars with broader emission associated with a CM. For O-type stars, the high mass-loss rates are sufficient to accumulate enough material for line emission even within the relatively short free-fall time-scale associated with a DM: this high mass-loss rate also leads to a rapid magnetic spindown of the stellar rotation. For the B-type stars, the longer confinement of a CM is required to accumulate sufficient emitting material from their relatively weak winds, which also lead to much longer spindown time-scales. Finally, we discuss how other observational diagnostics, e.g. variability of UV wind lines or X-ray emission, relate to the inferred magnetic properties of these stars, and summarize prospects for future developments in our understanding of massive-star magnetospheres.