A dynamical magnetosphere model for periodic Halpha emission from the slowly rotating magnetic O star HD191612

Jon O. Sundqvist(1), Asif ud-Doula(2), Stanley P. Owocki(1), Richard H. D. Townsend(3), Ian D. Howarth(4), Gregg A. Wade(5), and the MiMeS Collaboration

1 - University of Delaware, Bartol Research Institute, USA; 2 -Penn State Worthington Scranton, USA; 3 University of Wisconsin, Department of Astronomy, USA; 4 - University College London, Department of Physics and Astronomy, United Kingdom; 5 - Royal Military College of Canada, Department of Physics, Kingston, Canada

The magnetic O-star HD191612 exhibits strongly variable, cyclic Balmer line emission on a 538-day period. We show here that its variable Halpha emission can be well reproduced by the rotational phase variation of synthetic spectra computed directly from full radiation magneto-hydrodynamical simulations of a magnetically confined wind. In slow rotators such as hd, wind material on closed magnetic field loops falls back to the star, but the transient suspension of material within the loops leads to a statistically overdense, low velocity region around the magnetic equator, causing the spectral variations. We contrast such ``dynamical magnetospheres'' (DMs) with the more steady-state ``centrifugal magnetospheres'' of stars with rapid rotation, and discuss the prospects of using this DM paradigm to explain periodic line emission from also other non-rapidly rotating
magnetic massive stars.

Reference: MNRAS letters, in press
Status: Manuscript has been accepted

Weblink: http://arxiv.org/abs/1203.1050


Email: jon@bartol.udel.edu