The V Sagittae Stars

Abstract

We identify a class of four Galactic stars with similar spectroscopic and photometric properties: V617 Sgr, HD 104994, WX Cen, and V Sge. We call this class the "V Sagittae stars." The characteristics and literature of each of these stars are reviewed. They show high‐ionization species like O vi and N v; the emission of He ii λ4686 is stronger than twice the strength of Hβ. The orbital periods vary from 5 to 12 hr, and the orbital light curve can have shapes of either double eclipse or sine wave. The close similarities of these objects to the supersoft X‐ray sources is pointed out. The nature of the compact star in these system is still an open question; white dwarfs, neutron stars, black holes, or carbon main‐sequence stars have been proposed.