双星与变星研究组知识库

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 x 10(-7) days yr(-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-3 sin i(3) = 0.52(+/- 0.07) M-circle dot 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 BVRcIc 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.