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} solar mass star with a radius of 7.0^{+2.4}_{-1.8} solar radii, and a relatively low mass-loss rate of 1.4^{+3.1}_{-0.95}x10^{-9} solar masses per year. The photospheric absorption lines are narrow, and we use the Fourier transform technique to infer vsin i=15\pm 3 km/s. This vsini implies a maximum rotational period of 31.5 days, 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} gauss. The derived field strength and wind characteristics imply a wind that is strongly confined by the magnetic field.

Preprints available at http://arxiv.org/pdf/0910.0214v1

For more information, contact the MiMeS Principal Investigator:

Gregg A. Wade

Professor of Physics

Royal Military College of Canada

(613) 541-6000 x 6140

MiMeS is part of the international MagICS collaboration.

Last updated: 26-Jun-09