TY - JOUR
T1 - A magnetic confinement versus rotation classification of massive-star magnetospheres
AU - Petit, V.
AU - Owocki, S. P.
AU - Wade, G. A.
AU - Cohen, D. H.
AU - Sundqvist, J. O.
AU - Gagne, M.
AU - Máiz Apellaniz, J.
AU - Oksala, M. E.
AU - Bohlender, D. A.
AU - Rivinius, T.
AU - Henrichs, H. F.
AU - Alecian, E.
AU - Townsend, R. H.D.
AU - Ud-Doula, A.
AU - Collaboration, Mi Me S.
N1 - Funding Information:
MIS acknowledges financial support from a Jean Rogerson Scholarship, a UWA Top-up Scholarship from the University of Western Australia, and a CSIRO Malcolm McIntosh Lecture bankmecu scholarship. MIS thanks the Astronomical Society of Australia for providing financial support via a Student Travel Award, which enabled furthered collaboration on this paper, and also Lawrence Berkeley National Laboratory for hosting her during part of this work. CB and TMD acknowledge the support of the Australian Research Council through the award of Future Fellowships, grants FT110100639 and FT100100595, respectively. The Centre for All-sky Astrophysics is an Australian Research Council Centre of Excellence, funded by grant CE110001020.
PY - 2013/2/11
Y1 - 2013/2/11
N2 - 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 Alfv́en 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, versus dynamical magnetospheres (DM), with RK > RA. We show how key observational diagnostics, like the presence and characteristics of Ha 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 Ha 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 CMis 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
AB - 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 Alfv́en 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, versus dynamical magnetospheres (DM), with RK > RA. We show how key observational diagnostics, like the presence and characteristics of Ha 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 Ha 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 CMis 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
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U2 - 10.1093/mnras/sts344
DO - 10.1093/mnras/sts344
M3 - Article
AN - SCOPUS:84873921970
SN - 0035-8711
VL - 429
SP - 398
EP - 422
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 1
ER -