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Discovery of a magnetic field in the O9 sub-giant star HD 57682 by the MiMeS Collaboration | J.H. Grunhut
; G.A. Wade
; W.L.F. Marcolino
; V. Petit
; H.F. Henrichs
; D.H. Cohen
; E. Alecian
; D. Bohlender
; J.-C. Bouret
; O. Kochukhov
; C. Neiner
; N. St-Louis
; R.H.D. Townsend
; MiMeS Collaboration
; | Date: |
1 Oct 2009 | Abstract: | We report the detection of a strong, organised magnetic field in the O9IV
star HD 57682, using spectropolarimetric observations obtained with ESPaDOnS at
the 3.6-m Canada-France-Hawaii Telescope within the context of the Magnetism in
Massive Stars (MiMeS) Large Program. From the fitting of our spectra using NLTE
model atmospheres we determined that HD 57682 is a $17^{+19}_{-9}$ M$_{odot}$
star with a radius of $7.0^{+2.4}_{-1.8}$ R$_odot$, and a relatively low
mass-loss rate of $1.4^{+3.1}_{-0.95} imes10^{-9}$ M$_{odot}$ yr$^{-1}$. The
photospheric absorption lines are narrow, and we use the Fourier transform
technique to infer $vsin i=15pm3$ km s$^{-1}$. This $vsin i$ implies a
maximum rotational period of 31.5 d, a value qualitatively consistent with the
observed variability of the optical absorption and emission lines, as well as
the Stokes $V$ profiles and longitudinal field. Using a Bayesian analysis of
the velocity-resolved Stokes $V$ profiles to infer the magnetic field
characteristics, we tentatively derive a dipole field strength of
$1680^{+134}_{-356}$ G. The derived field strength and wind characteristics
imply a wind that is strongly confined by the magnetic field. | Source: | arXiv, 0910.0214 | Services: | Forum | Review | PDF | Favorites |
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