Reference : Confirmation of the magnetic oblique rotator model for the Of?p star HD 191612
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/99761
Confirmation of the magnetic oblique rotator model for the Of?p star HD 191612
English
Wade, G. A. [Department of Physics, Royal Military College of Canada, PO Box 17000, Stn Forces, Kingston, Ontario K7K 7B4, Canada]
Howarth, I. D. [Department of Physics and Astronomy, UCL, Gower Place, London WC1E 6BT]
Townsend, R. H. D. [Department of Astronomy, University of Wisconsin-Madison, 475 N. Charter Street, Madison, WI 53706-1582, USA]
Grunhut, J. H. [Department of Physics, Royal Military College of Canada, PO Box 17000, Stn Forces, Kingston, Ontario K7K 7B4, Canada; Department of Physics, Engineering Physics and Astronomy, Queen's University, 99 University Avenue, Kingston, Ontario K7L 3N6, Canada]
Shultz, M. [Department of Physics, Royal Military College of Canada, PO Box 17000, Stn Forces, Kingston, Ontario K7K 7B4, Canada; Department of Physics, Engineering Physics and Astronomy, Queen's University, 99 University Avenue, Kingston, Ontario K7L 3N6, Canada]
Bouret, J*-C [LAM-UMR 6110, CNRS & Université de Provence, rue Frédéric Joliot-Curie, F-13388 Marseille Cedex 13, France; NASA/GSFC, Code 665, Greenbelt, MD 20771, USA]
Fullerton, A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA]
Marcolino, W. [Observatório do Valongo, Universidade Federal do Rio de Janeiro, Ladeira Pedro Antônio 43, CEP 20080-090, Rio de Janeiro, Brazil]
Martins, F. [LUPM-UMR5299, CNRS & Université Montpellier II, Place Eugène Bataillon, F-34095 Montpellier, France]
Nazé, Yaël mailto [FNRS-Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 Aout, 17, Bat B5C B4000, Liège, Belgium]
Ud Doula, A. [Penn State Worthington Scranton, 120 Ridge View Drive, Dunmore, PA 18512, USA]
Walborn, N. R. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA]
Donati, J.-F. [Observatoire Midi-Pyrénées, 14 avenue Édouard Belin, F-31400 Toulouse, France]
1-Oct-2011
Monthly Notices of the Royal Astronomical Society
Blackwell Publishing
416
3160-3169
Yes (verified by ORBi)
International
0035-8711
Oxford
United Kingdom
[en] stars: individual: HD 191612 ; stars: magnetic field ; stars: massive ; stars: rotation
[en] This paper reports high-precision Stokes V spectra of HD 191612 acquired using the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope, in the context of the Magnetism in Massive Stars (MiMeS) Project. Using measurements of the equivalent width of the Hα line and radial velocities of various metallic lines, we have updated both the spectroscopic and orbital ephemerides of this star. We confirm the presence of a strong magnetic field in the photosphere of HD 191612, and detect its variability. We establish that the longitudinal field varies in a manner consistent with the spectroscopic period of 537.6 d, in an approximately sinusoidal fashion. The phases of minimum and maximum longitudinal field are, respectively, coincident with the phases of maximum and minimum Hα equivalent width and H[SUB]p[/SUB] magnitude. This demonstrates a firm connection between the magnetic field and the processes responsible for the line and continuum variability. Interpreting the variation of the longitudinal magnetic field within the context of the dipole oblique rotator model, and adopting an inclination i= 30° obtained assuming alignment of the orbital and rotational angular momenta, we obtain a best-fitting surface magnetic field model with obliquity β= 67°± 5° and polar strength B[SUB]d[/SUB]= 2450 ± 400 G. The inferred magnetic field strength implies an equatorial wind magnetic confinement parameter η[SUB]*[/SUB]≃ 50, supporting a picture in which the Hα emission and photometric variability have their origin in an oblique, rigidly rotating magnetospheric structure resulting from a magnetically channelled wind. This interpretation is supported by our successful Monte Carlo radiative transfer modelling of the photometric variation, which assumes the enhanced plasma densities in the magnetic equatorial plane above the star implied by such a picture, according to a geometry that is consistent with that derived from the magnetic field. Predictions of the continuum linear polarization resulting from Thompson scattering from the magnetospheric material indicate that the Stokes Q and U variations are highly sensitive to the magnetospheric geometry, and that expected amplitudes are in the range of current instrumentation.
Researchers ; Professionals
http://hdl.handle.net/2268/99761
10.1111/j.1365-2966.2011.19265.x
http://cdsads.u-strasbg.fr/abs/2011MNRAS.416.3160W
http://de.arxiv.org/abs/1106.3008

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