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

TL;DR

This study reports the detection of a centrifugal magnetosphere around the He-strong magnetic B1 star ALS 3694, based on spectropolarimetric observations revealing a stable strong magnetic field and variable H-alpha emission.

Contribution

First detection of a centrifugal magnetosphere around a He-strong magnetic B1 star using spectropolarimetric data.

Findings

Stable approximately 2 kG magnetic field over 6 nights

Variable H-alpha emission peaking at high velocities

Presence of a centrifugal magnetosphere inferred from emission profiles

Abstract

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 ($\sim 3 v\sin{i}$). 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.