Multiplicity of A-type and related stars

Abstract

The origin of chemically peculiar stars remains enigmatic, especially regarding their frequency among their "normal" peers. In addition to magnetic fields and rotation, multiplicity may shed light on the question. We mention the main surveys of the three kinds performed so far of intermediate mass stars, either normal or chemically peculiar, magnetic or not: imaging, spectroscopic, and photometric. We also consider the mulitiplicity of red giant stars, since many of them are descendants of A-type stars, through Mermilliod's radial velocity monitoring of open cluster members. We briefly review the orbital properties of binary systems hosting chemically peculiar stars. Some specific objects of special interest are mentioned as deserving further study. Finally, we recall that some binary systems composed of A-type stars are progenitors of Type Ia supernovae, and evoke the potentialities of future surveys like Gaia.