A new time series of high-resolution Stokes I and V spectra of the magnetic B2V star HD 184927 has been obtained in the context of the Magnetism in Massive Stars ( MiMeS ) Large Program with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope and dimaPol liquid crystal spectropolarimeter at 1.8-m telescope of Dominion Astrophysical Observatory .
We model the optical and UV spectrum obtained from the IUE archive to infer the stellar physical parameters .
Using magnetic field measurements we derive an improved rotational period of 9.53102 \pm 0.0007 d. We infer the longitudinal magnetic field from lines of H , He and various metals , revealing large differences between the apparent field strength variations determined from different elements .
Magnetic Doppler Imaging using He and O lines yields strongly nonuniform surface distributions of these elements .
We demonstrate that the diversity of longitudinal field variations can be understood as due to the combination of element-specific surface abundance distributions in combination with a surface magnetic field that is comprised of dipolar and quadrupolar components .
We have reanalyzed IUE high resolution spectra , confirming strong modulation of wind-sensitive C iv and S iv resonance lines .
However , we are unable to detect any modulation of the H \alpha profile attributable to a stellar magnetosphere .
We conclude that HD 184927 hosts a centrifugal magnetosphere ( \eta _ { * } \sim 2.4 ^ { +22 } _ { -1.1 } \times 10 ^ { 4 } ) , albeit one that is undetectable at optical wavelengths .
The magnetic braking timescale of HD 184927 is computed to be \tau _ { J } = 0.96 or 5.8 Myr .
These values are consistent with the slow rotation and estimated age of the star .