TIC 9066956.01: a 2.6 Earth-radius planet candidate on a 0.71-day orbit around a nearby M dwarf, found in TESS full-frame images

We report a transiting planet candidate around TIC 9066956 (Gaia DR3 2432763248476007296), a T = 13.9 M dwarf at 89.5 pc, found by Tessa, an open search of TESS full-frame-image light curves of nearby K and M dwarfs that were mostly never observed at 2-minute cadence. Data from 6 sectors show 174 transits with period P = 0.713448 ± 0.000001 d, depth 4661 ppm and duration 0.79 h (SNR 17.6), implying a planet radius of 2.65+0.16−0.08 R⊕. The signal passes these tests: odd and even transits agree (0.7σ) and there is no significant secondary eclipse (SNR 2.2); the depth is consistent across sectors (p = 0.91); difference imaging places the source on the target (0.6″ ± 1.5″, 6 sectors) and on none of the 8 Gaia neighbours bright enough to fake it; Gaia DR3 astrometry (RUWE 1.10) shows no sign that the target is a binary; in a leave-one-season-out test, each of 5 seasons is predicted from the others and shows the dip at the predicted times; the identical search on this star's upside-down light curve finds nothing stronger than SNR 6.5, against 17.6 for the dip; TRICERATOPS gives FPP = 0.050 and NFPP = 1.4e-09: a likely planet (FPP < 0.5 and NFPP < 0.001; Giacalone et al. 2021), short of the statistical-validation bar (FPP < 0.015, NFPP < 0.001). The stellar density implied by the transit shape is higher than the catalogue value (ratio 2.45, 68% interval 1.31–2.83); see Caveats. The candidate matches no known planet, TOI, CTOI, catalogued eclipsing binary or variable star. Other searches have also reported it (PHANTOM (Benoit 2026, doi 10.5281/zenodo.23584959)); Tessa found it independently, and this note adds its own vetting and predictions. We give an ephemeris and predicted transit times (timing uncertainty ≈2 min) for TESS Sector 134, which observes the star from 2028-08-16 to 2028-09-12, and for ground-based observations, and set out in advance the criterion by which new data will test the prediction. Files: the preprint (PDF); every predicted transit to 2027-06-30, with ground-site observability (CSV); and the candidate parameters (JSON).