HgMn Stars: Cornerstones for our Understanding of Late B-type Multiple Star Formation

Abstract

The most distinctive feature of HgMn stars is the extreme overabundance of heavy elements in their atmospheres. Furthermore, they show chemical horizontal and vertical inhomogeneities and kG mean quadratic magnetic fields. The topology of these magnetic fields should be rather complex, as we measure only weak mean longitudinal magnetic fields. The connection between these features and their membership in binary and multiple systems is supported by our observations during the last decade. The most important result achieved in our studies of a large sample of late B-type primaries in spectroscopic binaries and visual multiples is the finding that the vast majority of slowly rotating late B-type stars formed in binary systems with v sin i < 70 km s^{-1} and orbital periods between 3 and 20 days become HgMn stars.