TESS data from 2018 to 2026 show eclipse depth changes of 5% or more in 11 of 301 eclipsing binaries near the south ecliptic pole, including a new triple, TIC 300560295

We measured the eclipse depths of eclipsing binaries (EBs) in the southern TESS continuous viewing zone in each sector from 2018 to 2026 (sectors 1 to 98). A change in eclipse depth shows that the orbit of the binary changes its orientation. Usually a third body causes this. The input was 518 EBs from the TESS EB catalogue of Prša et al. (2022) and 9358 SPOC 2-min light curves. 301 EBs had a Year-1 reference and data from at least one later year. A template fit flagged 65 eclipses in 50 EBs with a depth change of 5% or more at 5 sigma or more. We examined each flagged eclipse again with a model-free depth measurement, an aperture (blend) test and a visual check. 13 eclipses in 11 EBs passed all tests. One of the 11 EBs is the known control, TIC 167692429. Its secondary eclipse disappears, as Borkovits et al. (2020) found. The other 10 EBs are new detections of depth changes at the 5-80% level. AE Pic (TIC 150442264) shows apsidal motion. The secondary eclipse moves toward the primary eclipse by 2.71 +/- 0.18 min/yr (14.7 sigma), and the two eclipse depths change in opposite directions. Two circular binaries, AR Dor and WZ Pic, give null tests with no significant change. TIC 300560295 (TYC 9179-01083-1) is a new hierarchical triple. Its primary eclipse depth increased from 2.6% to 4.8%, and its secondary eclipse depth increased from 0.19% to 1.1%. The eclipse widths also increased. Thus the cause is a change of the inner orbit, not a change of dilution. The eclipse times show a light-travel-time effect with a period of 2047 +/- 26 d. This orbit agrees with the independent Gaia DR3 astrometric acceleration solution. A test with 71 shifted orbital phases gave an equal agreement for only 1 phase. A forward model uses the Gaia magnitude, colour, photocentre orbit and RV scatter, and dwarf-star relations. It shows that a third star of about 1.13 solar masses (near F9 V) gives about 93% of the G-band light. Limitations: the survey uses only stars with 2-min light curves and Year-1 data. The visual check is subjective. Spots can change small depths. We did not fit a dynamical model, and spectra must confirm the triple. The package contains the code, the derived tables, the figures and the instructions to reproduce all results.

eclipsing binaries · eclipse depth variations · TESS · continuous viewing zone · south ecliptic pole · hierarchical triple stars · light-travel-time effect · apsidal motion · orbital precession · Gaia DR3 astrometry · Gaia DR3 acceleration solution · AE Pic · TIC 300560295 · TIC 167692429 · model-free vetting · aperture blend test · eclipse timing · survey