TIC 38699429: an unconfirmed transit candidate around a faint nearby M dwarf, from a hash-registered search of public TESS-SPOC light curves

We report an unconfirmed transit candidate on TIC 38699429 (Gaia DR3 4676612253064169344; Tmag 15.27, Teff about 2914 K, d about 57 pc), a faint nearby M dwarf with 31 TESS-SPOC full-frame light curves (Sectors 1-69) and no 2-min data. The signal has P = 11.718179 d, a template depth of 24621 +/- 893 ppm (about 2.5 %) and a measured duration of about 1.4 h. It was the only survivor of a hash-registered coherent multi-sector search of 400 M dwarfs without 2-min data (the design was hashed before the real data were searched; the time stamps were generated by the analysis session, and the Zenodo record post-dates the run); the threshold comes from 110 control stars and 331 scrambled runs (at most 0.05 expected false positives for the noise in the scrambled data). The ephemeris was written to file before Sectors >= 86 were looked at (its hash was recorded in a hash file only afterwards), and the signal is recovered there (z = 10.8). A blind reproduction and a counter-evidence analysis, both by AI instances of the same model family using the same photons, find it real, periodic and located on or near the target. It is not validated: TRICERATOPS FPP 0.19, NFPP 0.16; the pixel position test has only moderate power (p = 0.087) and its best position is 5.7 arcsec from the Gaia position; a bound faint companion, an unresolved background eclipsing binary and a twin eclipsing binary at twice the period are not excluded; the radius of about 2.8 Earth radii holds only for a single star. The signal is also already a public SPOC data-validation TCE (generated 2024-09-14, multi-sector run S56-S69) although the star is not a TOI or CTOI as of 2026-10-25; no claim of first detection is made.

Author statement (25 October 2026): the author checked all figures, data sources and analyses of this note himself, ran them in his own Python environment and verified the results, and ran the AI-written scripts in his own Python environment (correction of 26 October 2026: an earlier wording of this sentence said that he also recomputed the values and figures in separate code of his own; that claim is withdrawn, see Version 3); the conclusions and, in outline, the methodology are his. The search, the analysis and the draft were executed with the AI system Claude (Anthropic) in several instances; the reviewers are AI instances, not independent human replications.

Version 2 (25 October 2026) corrects the time labels of Sect. 3.5 (local time had been labelled as UTC), the sample counts, citations and the author statement; no result changed (see VERSION_NOTES.txt in the supplement).