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Paper: The Geometry of the Magnetosphere of θ1 OrionisC
Volume: 337, The Nature and Evolution of Disks Around Hot Stars
Page: 305
Authors: Smith, M.A.; Fullerton, A.W.
Abstract: As a suspected hot analog to the Bp stars, θ1 OrionisC (O6—7V) has UV resonance lines that modulate over the rotation cycle. But do these variations follow the patterns expected from absorptions and emissions formed in a flattened corotating magnetosphere? In this paper we report that the observed variations are quite different from the Bp paradigm. For example, the far-blue wings of the CIV and NV doublets, formed by a fully accelerated wind, are anticorrelated with respect to the fluxes in the red half of the profiles. An observer viewing the magnetosphere edge-on sees profiles with both a depressed far-blue wing and elevated red wing. An examination of strong, excited NIV and OV lines demonstrates this same behavior. The relative changes in these line strengths are consistent with an optically thick medium not far from thermal equilibrium. We argue that the elevated red-profile fluxes arise from emission seen against the star by post-shock wind matter returning to the star. Following new MHD simulations by ud-Doula, this may correspond to hot blobs condensing in the magnetic plane and heated by ram pressure as they fall back to the star along the same magnetic lines that guided them to the equator. One corollary of our work is that there is no evidence for a static cooling disk.
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