V752 Cen – a triple-lined spectroscopic contact binary with sudden and continuous period changes

Abstract

V752 Cen is a triple-lined spectroscopic contact binary. Its multicolour light curves were obtained in the years 1971 and 2018, independently. Photometric analyses reveal that the two sets of light curves produce almost consistent results. It contains a W-subtype totally eclipsing binary, and its mass ratio and fill-out factor are q = 3.35(1) and f = 29(2) per cent. The absolute elements of its two-component stars were determined to be M1 = 0.39(2) M, M2 = 1.31(7) M, R1 = 0.77(1) R, R2 = 1.30(2) R, L1 = 0.75(3) L, and L2 = 2.00(7) L. The period of V752 Cen is 0.37023198 d. The 0.37-d period remained constant from its first measurement in 1971 until the year 2000. However, it changed suddenly around the year 2000 and has been increasing continuously at a rate of dP/dt = +5.05 × 10−7 d yr−1 since then, which can be explained by mass transfer from the less massive component star to the more massive one with a rate of ddMt2 = 2.52 × 10−7 M yr−1. The period variation of V752 Cen over the 48 yr in which the period has been monitored is really unusual, and is potentially related to effects from the possible presence of a nearby third star or of a pair of stars in a second binary.