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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$α$ line displays variable emission on all nights, peaking at high velocities ($\sim 3 v\sin{i}$). Given the presence of a strong ($B_{\rm 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.