TESS data to 2026 confirm 16 of 24 published delta Scuti pulsation-timing orbits and change 8 periods; Gaia DR3 orbits agree with the new periods for 6 of 7 stars

We tested the 51 phase-modulation (PM) binary stars of Dholakia et al. (2025), which came from TESS 2-min data of 2018 to 2022 (sectors 1 to 55). We measured the phases of up to 8 delta Scuti modes in 5-day segments and fit light-travel-time orbits to the wrapped phases. First, we fit the published orbits to the sector 1 to 55 data and forecast the phases in sectors 56 to 98 (September 2022 to January 2026), with 1,243 SPOC 2-min and 480 TESS-SPOC FFI light curves. For the 24 solved orbits, 75 percent of test sectors were within 3 sigma of the forecast in the first year, but only 43 percent after two years. Intrinsic phase drift that is different for each mode causes most failures. This drift is significant in 40 of 51 stars. Second, we refit all data (up to 7.4 years) with an orbit plus per-mode drift. The data agree with 16 of the 24 published solved periods. Four periods change by 2 to 8 percent, and four change much more: TIC 219776919 140.7 d (not 185 d), TIC 306773428 155.3 d (not 188.3 d), TIC 219810122 804 d (not 398 d) and TIC 41258067 409 d (not 368 d). Third, we compared the orbits with Gaia DR3 non-single-star orbits, which are independent. Our periods agree with Gaia within 1.1 percent for 6 of 7 stars with Gaia orbits above 20 d. Only 2 of the 6 published periods agree. We also give new orbits for TIC 229751802 (217.3 d; Gaia 217.6 d), 229954300 (58.3 d), 288241831 (798 d) and 350622144 (1632 d). Limitations: the paper gives no omega or orbital phase, so we refit them from the published P, a1 sin i and e. Formal errors do not include drift-model error, 33 stars have no data after sector 86, and long orbits stay poorly constrained. Two short-period Gaia SB solutions (0.86 d and 0.88 d) have no TESS counterpart and are probably pulsation artefacts. For two stars, the Gaia RV scatter is far below the TESS orbit prediction, which can be a blend; we did not test this.

delta Scuti stars · phase modulation · pulsation timing · light travel time · binary stars · TESS · Gaia DR3 · non-single stars · forecast test · replication · orbit periods