A baseline change reverses free-tail timing curvature for KOI-2700 in Kepler Q1 to Q16

We test whether a changing dust tail and baseline choice can bias transit timing for KOI-2700. Free-tail fits to Kepler release 25 Q1 to Q16 aperture flux give an apparent period rate of -1.226 seconds per year with linear per-orbit baselines and +0.739 seconds per year with quadratic baselines. Conditional 95 percent block intervals are [-1.908, -0.453] and [0.343, 1.393]. The same exposures thus give opposite curvature signs under these choices. Removing the short first quarter makes both free-tail rates negative. This prevents a stable orbital interpretation. A separate constant-time signal with a tail scale that falls from 0.07 to 0.04 orbital phase gives 8.62 minutes of false timing range with a fixed-tail fit at the actual exposure times. A free-tail fit recovers that input time within 8.8 seconds. The synthetic tail change does not explain the full measured curve. We also test corrected flux, ingress width, detector seasons, and quarter omissions. The intervals depend on 12-orbit blocks, finite parameter bounds, and a descriptive profile. Poor profile fits, residual stellar variation, dust geometry, and instrument response limit physical claims. No new planet, orbital evolution, or independent telescope confirmation is established. Code, aggregate profiles, bootstrap fits, hashes, figures, and separate-scratch reproduction steps are included.

astronomy · KOI-2700 · KIC 8639908 · Kepler · dust tail · transit timing · model bias · null discovery result