中国科学院云南天文台机构知识库

New photometry for two Algol-type binaries, EU Hya (P = 0.7782 d) and AW Vul (P = 0.8065 d), was carried out using the 60-cm telescope at Xinglong station of National Astronomical Observatories, Chinese Academy of Sciences. With the updated Wilson-Devinney code, photometric elements were derived from the multi-color light curves. The modeled results indicate that the two systems are near-contact binaries, whose secondary components fill their Roche lobes. The fill-out factors of the primaries are f(p) = 81.2 (+/- 0.2) % for EU Hya and f(p) = 82.4 (+/- 0.3) % for AW Vul. Period analysis implies that there exists a downward parabola with a light-time orbit from the (O - C) curve. This kind of periodic oscillation may be attributed to the light-time orbit effect of a third companion. The long-term period decrease may be caused by mass and angular momentum loss. When the orbital period decreases, the fill-out factor of f(p) will increase. Our results indicate that the primaries will also eventually fill their Roche lobes. EU Hya and AW Vul may possibly evolve from semi-detached binaries into contact ones.