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Revisiting the Rigidly Rotating Magnetosphere model for inline image Ori E – I. Observations and data analysis

Authors

  • M. E. Oksala,

    Corresponding author
    1. Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA
    2. Department of Physics, Royal Military College of Canada, PO Box 17000, Station Forces, Kingston, Ontario K7K 7B4, Canada
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  • G. A. Wade,

    1. Department of Physics, Royal Military College of Canada, PO Box 17000, Station Forces, Kingston, Ontario K7K 7B4, Canada
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  • R. H. D. Townsend,

    1. Department of Astronomy, University of Wisconsin-Madison, 2535 Sterling Hall, 475 N Charter Street, Madison, WI 53706, USA
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  • S. P. Owocki,

    1. Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA
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  • O. Kochukhov,

    1. Department of Physics and Astronomy, Uppsala University, Box 516, Uppsala 75120, Sweden
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  • C. Neiner,

    1. LESIA, UMR 8109 du CNRS, Observatoire de Paris, UPMC, Université Paris Diderot, 5 place Jules Janssen, 92195 Meudon Cedex, France
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  • E. Alecian,

    1. LESIA, UMR 8109 du CNRS, Observatoire de Paris, UPMC, Université Paris Diderot, 5 place Jules Janssen, 92195 Meudon Cedex, France
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  • J. Grunhut,

    1. Department of Physics, Royal Military College of Canada, PO Box 17000, Station Forces, Kingston, Ontario K7K 7B4, Canada
    2. Department of Physics, Engineering Physics and Astronomy, Queen’s University, Kingston, Ontario K7L 3N6, Canada
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  • the MiMeS Collaboration


Based on observations obtained using the Narval spectropolarimeter at the Observatoire du Pic du Midi (France) which is operated by the Institut National des Sciences de l’Univers (INSU), observations obtained at the Canada–France–Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii, and observations collected at the European Organization for Astronomical Research in the Southern hemisphere, Chile, under programme ID 62.H-0319 and during the FEROS Commissioning run II.

E-mail: meo@udel.edu

ABSTRACT

We have obtained 18 new high-resolution spectropolarimetric observations of the B2Vp star σ Ori E with both the Narval and ESPaDOnS spectropolarimeters. The aim of these observations is to test, with modern data, the assumptions of the Rigidly Rotating Magnetosphere (RRM) model of Townsend & Owocki, applied to the specific case of σ Ori E by Townsend, Owocki & Groote. This model includes a substantially offset dipole magnetic field configuration, and approximately reproduces previous observational variations in longitudinal field strength, photometric brightness and Hα emission. We analyse new spectroscopy, including H i, He i, C ii, Si iii and Fe iii lines, confirming the diversity of variability in photospheric lines, as well as the double S-wave variation of circumstellar hydrogen. Using the multiline analysis method of least-squares deconvolution (LSD), new, more precise longitudinal magnetic field measurements reveal a substantial variance between the shapes of the observed and RRM model time-varying field. The phase-resolved Stokes V profiles of He i 5876 and 6678 Å lines are fitted poorly by synthetic profiles computed from the magnetic topology assumed by Townsend et al.. These results challenge the offset dipole field configuration assumed in the application of the RRM model to σ Ori E, and indicate that future models of its magnetic field should also include complex, higher order components.

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