PHANTOM Candidate TIC 38699429: An 11.71815-Day Transit Signal in TESS Photometry

Status: planet candidate. A periodic transit-like signal on TIC 38699429 found by PHANTOM (Planet Hunting Across Noisy TESS Observations and Measurements), an independent search of NASA TESS photometry. It has not been confirmed as a planet: its source star and nature are not yet established by follow-up observations (see Unresolved). Version 1.4 of this record. Changes in version 1.4 Version 1.4 adds pixel views of individual transits, color scales and apertures on the pixel views, and a search for a secondary eclipse; the conclusion, the adopted values and the results of version 1.3 are unchanged: Individual transits, pixel by pixel (analysis__events_1950_s<sector>.png, analysis__events_1950_2026-11-03.json and analysis__events_1950.py): six single transits, chosen by a rule fixed before any view was made (the 6 transits with the highest individual S/N in the searched light curve without sector 87, at most one per sector, each with at least five points in transit: sectors 28, 62, 69, 88, 96 and 98). For each, the direct and difference images of that transit alone, the transit's light curve in PHANTOM's PSF photometry and in the apertures' summed pixels, and the light curves of the central 7×7 pixels through it, in e⁻/s and 20-minute bins, and again (analysis__events_1950_s<sector>_pixels.png) every frame a half day either side, each pixel normalized to its own median, the frames colored by the pixel's brightness and the apertures marked. These views test whether individual events show a flux deficit near the target or near a resolved neighbor: in four of the six the difference image's largest deficit is in the target's pixel (3.7-7.7 times its error), in one in an adjacent pixel inside the apertures, and in sector 69, the transit with the highest light-curve S/N, the difference image is inconclusive (the target pixel's deficit 2.7 times its error, the largest deficit, four pixels away, 1.9; Detailed review). Color scales and apertures on every pixel view, the folded ones of version 1.3 included (redrawn from the same data; their numbers are unchanged): each image's scale in e⁻/s, the 3×3-pixel aperture of PHANTOM's (and TGLC's) aperture flux outlined, and TESS-SPOC's aperture where TESS-SPOC made a light curve (sectors 28, 62, 68 and 69 of those shown); in the pixel maps, the aperture pixels marked. A secondary eclipse (analysis__phase05_1950.png, analysis__phase05_1950_2026-11-04.json and analysis__phase05_1950.py): no secondary eclipse is detected at phase 0.5 (170 ± 780 ppm; for the box statistic used, a nominal white-noise 3σ upper limit of 2,490 ppm, about 9% of the transit's depth). Across phases 0.30 to 0.70 the highest-significance dip, at phase 0.31, is 3.2σ on white-noise errors and 2.6σ against the light curve's own scatter at 414 comparison phases; with about 84 independent phases tried, the scan finds no convincing secondary eclipse (Detailed review). These are visual and statistical diagnostics added to the record; the quantitative localization (Location of the dip), the fits and the TRICERATOPS results are those of version 1.2. Also in this version, wording, labeling and metadata changes, none of which changes a result: Location of the dip names the difference images' sign correctly (out-of-transit minus in-transit; version 1.3 said the reverse) and lists the 5 stars beyond 42″ the fitted position also excludes; the TRICERATOPS table marks NFPP values stored as exactly 0.0, and its automated-run row says where that result is kept; the TRICERATOPS paragraph gives each set-up's own FPP range in place of means, the scenarios each set-up's saved runs share (STP and EBx2P), the PTP and TP shares as labeled averages over the runs, the two scalar depths supplied (30,378 and 25,284 ppm), and the 30-min sectors' place (left out of the fitted light curve, included in the all-sector depth); Data and methods states that both set-ups fit PHANTOM's aperture light curve of the same six sectors and differ only in the depth, and what the 'label' field in the analysis__fpp files means; the transit-count paragraph and the depth comparison under Vetting are reworded (the latter's signed differences, and that its comparisons share data); Unresolved says "transiting object's mass" and gives the FPP as the observed run-to-run range; candidate.json adds light_curve_sectors (the sectors of each photometry in lightcurve.csv) and prior_detections_note, and its unresolved_neighbours_note now gives 31″ (10″ before), the separation within which two-source fits are used. TIC: 38699429 Star: Tmag 15.27, Teff 2914 K, radius 0.166 ± 0.005 R☉, distance 57.5 pc (TIC v8) Period: 11.7181493 ± 0.0000090 d Mid-transit epoch: BJD_TDB 2459970.07015 ± 0.00065 Depth: 26,349 ± 1,247 ppm Duration: 1.346 ± 0.059 h Radius if on the target: 2.81 +0.11/−0.10 R⊕ (physical fit's Rp/Rs × the TIC stellar radius, both uncertainties); not included: in the same sectors TGLC's light curves measure the transit 9-16% deeper than TESS-SPOC's (a radius about 5-7% larger), while PHANTOM's photometry agrees with TESS-SPOC within about 4%; and the TIC's contamination ratio (0.04) is uncertain, with brighter stars 2-2.5 pixels away Transits meeting the fit's coverage criterion: 82 in TESS sectors 1, 2, 3, 5, 6, 7, 8, 9, 10, 11, 12, 27, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 61, 62, 63, 64, 65, 66, 67, 68, 69, 88, 89, 90, 93, 94, 95, 96, 97, 98 Detection S/N: 33.7 (PHANTOM's search) Open questions (README.md, Unresolved): Which star the signal comes from; The irradiation, about 0.66 times Earth's, rests on the star's luminosity, known to about 28%; No radial-velocity measurement; Not statistically validated. The full record, with the evidence, uncertainties, data sources, cross-matches, unresolved questions and publication history, is README.md in this deposit.