The magnetic fields of the helium-weak B stars

Abstract

A survey of magnetic fields in 30 helium-weak B stars, one horizontal-branch B star, and one sdOB star has been conducted. Typical measurement errors for the He-weak stars are in the range of 100-400 gauss, and fields have been detected or confirmed in 12 stars, nine of which are known to belong to the Si and Sr-Ti He-weak spectroscopic subclasses. He-weak stars of these subclasses thus share with Ap stars and the He-strong stars the property of commonly showing detectable magnetic fields. However, the present observations are consistent with the view that the P-Ga He-weak stars are hotter analogs of the (nonmagnetic) Hg-Mn Ap stars, since none of the four P-Ga stars observed show detectable fields. The fraction of He-weak stars showing large fields appears to be larger than for Ap stars but smaller than for He-strong stars.