Discovery of a Centrifugal Magnetosphere Around the He-Strong Magnetic B1 Star ALS 3694

We report the results of 6 nights of Canada-France-Hawaii Telescope spectropolarimetric ESPaDOnS observations of the He-strong, magnetic B1 type star ALS 3694. The longitudinal magnetic field is approximately 2 kG in all 6 observations, showing essentially no variation between nights. The H$\alpha$ line displays variable emission on all nights, peaking at high velocities ($\sim 3v\sin i$). Given the presence of a strong ($B_{\mathrm{d}}>$6 kG) magnetic field, and the similarity of the emission profile to that of other magnetic B-type stars, we interpret the emission as a consequence of a centrifugal magnetosphere.