Five TESS dips toward TIC 221915858 support a 45.575-day interval if one source makes one comparable dip per cycle

Public TESS data contain five short dips toward TIC 221915858 in sectors 12, 39, 66, 93, and 102. Hawthorn et al. reported the first two. We measure all five and test 42 trial timing aliases near 729.2/n days, for n from 1 through 42. Only intervals near 45.57486 and 22.78743 days pass a 0.03-day timing tolerance. The shorter interval predicts an extra three-hour dip in sector 103. Independent image photometry gives a depth of 0.949 ppt with a working error of 0.301 ppt at that time. A grid of time, shape, and trend changes gives a maximum working three-error ceiling of 2.894 ppt. The data exclude a comparable 5-ppt dip under these tests. The longer interval has cycle numbers 0, 16, 32, 48, and 55. A linear fit gives 45.574856 days, with a working error of 0.000093 day and chi-square 12.01 for three degrees of freedom. The timing scatter limits precision. We avoid affected sector 102 and 103 QLP times by extracting independent pixel cutouts and applying an approximate target time correction. The interval result assumes one source and one comparable dip per cycle within the tested family. Close blends and a binary with two eclipses in a roughly 91.1497-day orbit remain possible. This work does not confirm a planet. The package preserves 12 input FITS files, provenance, original code, fit draws, checks, tables, figures, and reproduction instructions.

TESS · TIC 221915858 · duotransit · period aliases · transit timing · eclipsing binaries · public astronomical data · reproducible research