Magnetic fields of B and Herbig Ae stars measured with FORS1 at the VLT

Abstract

We present the results of a magnetic survey with FORS1 in polarimetric mode of a sample of B and Herbig Ae stars with previously undetected magnetic fields. For the first time a mean longitudinal magnetic field at a level higher than 3 sigma has been detected in one normal B star, two HgMn stars, one PGa star and four SPB stars. The observations of the three Herbig Ae stars (also known as Vega-like stars) reveal a definite longitudinal magnetic field in the star HD139614 at 4.8 sigma level: <B_z>=-450+-93 G. This is the largest magnetic field ever diagnosed for a Herbig Ae star. A hint of a magnetic field is found in the other two stars, HD144432 and HD144668, for which magnetic fields are measured at the ~1.6 sigma and ~2.5 sigma level respectively.