o Puppis: another Be plus sdO binary?

The spectrum of the Be star o Pup is shown to vary periodically with a period of 28.9 days. A radial-velocity variable He I 6678 angstrom emission component suggests that the star is the same type as phi Per, 59 Cyg, and FY CMa, i.e. binaries consisting of a Be star and a hot companion that illuminates the Be star disk (also called phi Per-type binaries or Be+sdO binaries). The range of radial-velocity variations of the stronger emission component in the helium line observed in o Pup is about 270 km s(-1), a value in good agreement with the range derived for phi Per-type binaries. The radial velocity curves defined by the prominent emission peak in He I 6678 angstrom line and H alpha + Paschen emission move in anti-phase. We suggest that o Pup is generically similar to phi Per-type systems and may represent the fourth case of a Be star with a hot subdwarf companion.