The radial velocity variations and evolutionary status of δ Lupi

The suspected β Cephei variable, δ Lupi, shows short term radial velocity variations of amplitude ∼ 4 km/s on a frequency of 5.046 c/d. These are superimposed on a longer term variation (16-19 days) of amplitude ∼ 20 km/s which we take to indicate that the star is a binary system. δ Lupi has a large v sin i (210 km/s) and this combined with the small mass function constrains the system to an extreme mass ratio, q ∼ 0.1, if the primary is rotating parallel to the axis of the orbit. Less extreme values are possible if inclinations of up to ∼ 20 deg between the axes are allowed. This situations also holds for another rapidly rotating, binary, β Cephei star V986 Ophiuchi. Both systems may contain white dwarf secondaries