摘要：VZ Lib is a southern triple-lined system. By analyzing all available times of light minima, orbital period changes are revisited in detail. We discovered that the observed–calculated (O −C) curve shows a long-term period decrease at a rate of dP dt 2.25 10 daysyr 7 1= - ´- -, revealing a mass transfer from the more massive component to the less massive one. A cyclic variation covering more than three cycles was discovered, which was analyzed for the light travel-time effect via the presence of the tertiary companion. The cyclic variation has a short period of 2.96 (±0.04) yr and a small semiamplitude of 0.0039 (±0.0004) days. The mass of the third body was determined to be M i sin 0.52 0.073 3 =( ) M e and an orbital semimajor axis shorter than 1.93 0.31( ) au was obtained. Orbital properties of this close-in companion should provide valuable information on the formation of close binaries and stellar dynamical interaction. New complete BVR I c c light curves of VZ Lib were obtained and modeled with the Wilson–Devinney code. The light curves show a small but significant O’Connell effect that was not detectable in 1981 and 2007 but in 2004, so we derived a new photometric solution with assuming spot and a third light in the system. It is found that the light-curve subtype changed from A-type to W-type, which was possibly caused by a dark spot on the massive component. Our photometric solutions are in agreement with the spectroscopic results given by previous authors.
