2011AJ....141..169B

We report the detection of a strong, reversing magnetic field and variable Hα emission in the bright helium-weak star HD 176582 (HR 7185). Spectrum, magnetic, and photometric variability of the star are all consistent with a precisely determined period of 1.5819840±0.0000030 days which we assume to be the rotation period of the star. From the magnetic field curve, and assuming a simple dipolar field geometry, we derive a polar field strength of approximately 7 kG and a lower limit of 52° for the inclination of the rotation axis. However, based on the behavior of the Hα emission, we adopt a large inclination angle of 85° and this leads to a large magnetic obliquity of 77°. The Hα emission arises from two distinct regions located at the intersections of the magnetic and rotation equators and which corotate with the star at a distance of about 3.5 R_* above its surface. We estimate that the emitting regions have radial and meridional sizes on the order of 2 R_* and azimuthal extents (perpendicular to the magnetic equator) of less than approximately 0.6 R_*. HD 176582 therefore appears to show many of the cool magnetospheric phenomena as that displayed by other magnetic helium-weak and helium-strong stars such as the prototypical helium-strong star σ Ori E. The observations are consistent with current models of magnetically confined winds and rigidly rotating magnetospheres for magnetic Bp stars.