[en] We report the detection of a strong, organized magnetic field in the secondary component of the massive O8III/I+O7.5V/III double-lined spectroscopic binary system HD 47129 (Plaskett's star) in the context of the Magnetism in Massive Stars survey. Eight independent Stokes V observations were acquired using the Echelle SpectroPolarimetric Device for the Observations of Stars (ESPaDOnS) spectropolarimeter at the Canada-France-Hawaii Telescope and the Narval spectropolarimeter at the Télescope Bernard Lyot. Using least-squares deconvolution we obtain definite detections of signal in Stokes V in three observations. No significant signal is detected in the diagnostic null (N) spectra. The Zeeman signatures are broad and track the radial velocity of the secondary component; we therefore conclude that the rapidly rotating secondary component is the magnetized star. Correcting the polarized spectra for the line and continuum of the (sharp-lined) primary, we measured the longitudinal magnetic field from each observation. The longitudinal field of the secondary is variable and exhibits extreme values of -810 ± 150 and +680 ± 190 G, implying a minimum surface dipole polar strength of 2850 ± 500 G. In contrast, we derive an upper limit (3σ) to the primary's surface magnetic field of 230 G. The combination of a strong magnetic field and rapid rotation leads us to conclude that the secondary hosts a centrifugal magnetosphere fed through a magnetically confined wind. We revisit the properties of the optical line profiles and X-ray emission - previously interpreted as a consequence of colliding stellar winds - in this context. We conclude that HD 47129 represents a heretofore unique stellar system - a close, massive binary with a rapidly rotating, magnetized component - that will be a rich target for further study.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Grunhut, J. H.; Department of Physics, Royal Military College of Canada, PO Box 17000, Stn Forces, Kingston, ON K7K 7B4, Canada ; Department of Physics, Engineering Physics and Astronomy, Queen's University, Kingston, ON K7L 3N6, Canada
Wade, G. A.; Department of Physics, Royal Military College of Canada, PO Box 17000, Stn Forces, Kingston, ON K7K 7B4, Canada
Leutenegger, M.; Department of Physics, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
Petit, V.; Department of Geology & Astronomy, West Chester University, West Chester, PA 19383, USA
Rauw, Grégor ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Sciences spatiales
Neiner, C.; LESIA, UMR 8109 du CNRS, Observatoire de Paris, UPMC, Université Paris Diderot, 5 place Jules Janssen, F-92195 Meudon Cedex, France
Martins, F.; LUPM-UMR5299, CNRS & Université Montpellier II, Place Eugène Bataillon, F-34095 Montpellier, France
Cohen, D. H.; Department of Physics and Astronomy, Swarthmore College, 500 College Ave, Swarthmore, PA 19081, USA
Gagné, M.; Department of Geology & Astronomy, West Chester University, West Chester, PA 19383, USA
Ignace, R.; Department of Physics and Astronomy, East Tennessee State University, Johnson City, TN 37663, USA
Mathis, S.; Laboratoire AIM Paris-Saclay, CEA/DSM-CNRS-Université Paris Diderot, IRFU/SAp Centre de Saclay, F-91191 Gif-sur-Yvette, France
de Mink, S. E.; Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA ; Johns Hopkins University, 3400 North Charles St, Baltimore, MD 21218, USA
Moffat, A. F. J.; Département de physique, Université de Montréal, CP 6128, Succursale Centre-Ville, Montréal, QC H3C 3J7, Canada
Owocki, S.; Bartol Research Institute, University of Delaware, Newark, DE 19716, USA
Shultz, M.; Department of Physics, Royal Military College of Canada, PO Box 17000, Stn Forces, Kingston, ON K7K 7B4, Canada ; Department of Physics, Engineering Physics and Astronomy, Queen's University, Kingston, ON K7L 3N6, Canada
Sundqvist, J.; Bartol Research Institute, University of Delaware, Newark, DE 19716, USA
MiMeS Collaboration; Bartol Research Institute, University of Delaware, Newark, DE 19716, USA)
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