Stellar motion causes most of the slow outer timing signal in TOI-4600 models with circular initial orbits

Can a slow transit timing signal in TOI-4600 occur when both planets start on circular orbits? We use public mass ratios and orbital elements from Table 7 of Hu et al. (2026). We define a controlled model with both orbits in the same plane and the observer in that plane. We integrate the Newtonian system for 20000 days. The outer planet has a fitted slow timing amplitude of 9.234 minutes at a period of 2954 days. The outer event can also use the center of mass of the star and inner planet as its reference. This change keeps the forces unchanged. It reduces the slow amplitude to 0.045 minute. The star displacement divided by the outer orbital speed predicts 9.279 minutes. Its pointwise estimate agrees with the paired timing shifts to within 0.14 second. Sampling the fast inner orbital motion once per outer orbit produces the slow alias. The inner planet has a fitted slow amplitude below 0.01 minute in this circular initial model. Large slow amplitudes return along a specified path to the published eccentricity components. This contribution tests known timing and sampling effects in specified TOI-4600 models. It includes all event times, code, source checks, and figures. It does not fit observed data or give limits for the true orbital eccentricities.

TOI-4600 · transit timing variations · stellar reflex motion · sampling alias · Jacobi coordinates · reproducible numerical experiment