Variable H$\alpha$ Emission and Absorption in Helium-Peculiar Stars
Session 45 -- Early Type Stars
Display presentation, Wednesday, 9:20-6:30, Heller Lounge Room

## [45.06] Variable H$\alpha$ Emission and Absorption in Helium-Peculiar Stars

D.A. Bohlender (CFHT), C.T. Bolton (DDO), G.M. Hill (UWO)

We are carrying out a program of high signal-to-noise, high resolution H$\alpha$ spectroscopy of a number of magnetic helium-strong and helium-weak stars with the Canada-France-Hawaii 3.6-m, Dominion Astrophysical Observatory 1.8-m, and David Dunlap Observatory 1.8-m telescopes. These observations have resulted in the discovery of several new spectrum variables, and include the first observations of variable H$\alpha$ emission and absorption in a number of helium-weak stars. In all cases, the spectrum variations have periods identical to the stars' rotation periods as derived from photometric or polarimetric observations. As has been suggested for the prototypical helium-strong star $\sigma$ Ori E, the H$\alpha$ variations apparently arise from the changing aspect of circumstellar material trapped in the magnetospheres of these peculiar stars.