2024MNRAS.531.3823Y

We reported the light curves (LCs) and orbital period variations of four short-period eclipsing binaries in the Southern hemisphere. From short-cadence time-series observations of the TESS, the intrinsic light changes rapidly with time. Δm_max and Δm_min exhibit random wave-like variations or quasi-periodicities. We deduced 14 sets of photometric solutions from the truncated LCs using the W-D programme. The results imply that V757 Cen and BC Gru are near-contact binaries, whose one or two components almost fill the Roche lobes with $f\gt 98{{\ \rm per\ cent}}$. Meanwhile, V535 Ara and AQ Tuc are A-subtype contact binaries. The asymmetric LCs were modelled by a cool spot assumed on a more massive component, which was used to track the stellar longitudes of star-spots. Based on all available eclipsing times (ETs), including 1495 ones from TESS LCs, the orbital period variations of four binaries were analysed. The (O - C) curves are coincidentally demonstrated by the light-time effect via the presence of the third bodies. The modulation periods approximate to 50 ∼ 60 yr. In the coplanar orbit with the central binaries, the third companions' masses are 0.105 M_⊙ for V757 Cen, 0.340 M_⊙ for BC Gru, 0.238 M_⊙ for V535 Ara, and 0.343 M_⊙ for AQ Tuc, whose systems are stable according to Harrington's criterion. Therefore, the four short-period eclipsing binaries, V757 Cen, BC Gru, V535 Ara, and AQ Tuc are hierarchical triple stellar systems.