SIMBAD references

The relation between the spin period (P_s) and the orbital period (P_o) in high-mass X-ray binaries is investigated. Be/X-ray binaries and SG/X-ray binaries occupy different areas in the Corbet diagram. The supergiant fast X-ray transients, IGR J18483–0311 and IGR J11215–5952, however, fall into the area occupied by Be/X-ray binaries. After excluding the other evolution scenarios, we find that the positions of the two supergiant fast X-ray transients in the diagram can be interpreted by being the descendants of O-emission X-ray binaries, i.e. the supergiant stars in these systems formed from O-type emission line stars instead of normal main-sequence stars. Therefore, we suggest that there are two types of SG/X-ray binaries: the first one is directly evolved from OB-type main-sequence star and neutron star systems without accretion history, and the other evolved from Be/X-ray binaries with accretion history.