  The recently discovered magnetic Herbig Ae and Be stars may provide
qualitatively new information about the formation and evolution of magnetic Ap
and Bp stars. We have performed a detailed investigation of one particularly
interesting binary system with a Herbig Ae secondary and a late B-type primary
possessing a strong, globally ordered magnetic field. Twenty high-resolution
Stokes V spectra of the system were obtained with the ESPaDOnS instrument
mounted on the CFHT. In these observations we see clear evidence for a magnetic
field in the primary, but no evidence for a magnetic field in the secondary. A
detailed abundance analysis was performed for both stars, revealing strong
chemical peculiarities in the primary and normal chemical abundances in the
secondary. The primary is strongly overabundant in Si, Cr, and other iron-peak
elements, as well as Nd, and underabundant in He. The primary therefore appears
to be a very young Bp star. In this context, line profile variations of the
primary suggest non-uniform lateral distributions of surface abundances.
Interpreting the 0.63995 +/- 0.00009 day variation period of the Stokes I and V
profiles as the rotational period of the star, we have modeled the magnetic
field geometry and the surface abundance distributions of Si, Ti, Cr and Fe
using Magnetic Doppler Imaging. We derive a dipolar geometry of the surface
magnetic field, with a polar strength of 1230 G and an obliquity of 57 degrees.
The distributions Ti, Cr and Fe are all qualitatively similar, with an
elongated patch of enhanced abundance situated near the positive magnetic pole.
The Si distribution is somewhat different, and its relationship to the magnetic
field geometry less clear.
