Circumstellar disks around Herbig Ae/Be stars: Polarization, outflows and binary orbits

Abstract

The geometrical relationship between the distribution of circumstellar matter, observed optical linear polarization, outflows and binary orbital plane in Herbig Ae/Be stars is investigated. Optical linear polarization measurements carried out for a number of Herbig Ae/Be stars that are either known to be in binary systems and/or have bipolar jets are presented in this paper. Available information on the position angles of polarization, outflows and binary companions for Herbig Ae/Be stars is compiled and analysed for any possible correlations. In ~85% of the sources the outflow position angle is within 30deg of being parallel or perpendicular to the polarization position angle. In ~81% of the sources the binary position angle is within 30deg of being parallel or perpendicular to the polarization position angle. Out of 15 sources with bipolar outflows, 10 sources have the binary position angle within 30deg of being perpendicular to the outflow position angle. These results favour those binary formation mechanisms in which the binary components and the disks around individual stars or circumbinary disks are coplanar.