1999A&A...349..511L

The recent eclipse of the long-period (P=7430^d) binary star VV Cephei is studied by means of UBV photometry and optical spectroscopy. Both photometry and variations of the emission lines (Hα and FeII λ 4233) show that the eclipse occured about 68 days later than predicted from the ephemeris. Such a sudden about 1% lengthening of the orbital period between the last two eclipses implies that the generally accepted model of VV Cep with the masses of both the M supergiant and the hot B star of about 20M_☉ should be revised. The period change due to mass transfer between the components or mass ejection from the VV Cep system can be explained, if one accepts the medium mass model for VV Cep, with the mass of the M star about 2.5M_☉ and of the B star about 8M_☉. This model implies that the cool component of VV Cep could be an AGB star rather than a supergiant.