The Sedna Anomaly and a Third Trans-Neptunian Perturber: A Perihelion-Lifting Sweep with ATMAN v5.0 (Paper VII)

(Abstract) We present a two-dimensional mass–distance sweep over a hypothetical third trans-Neptunian perturber (P3) with M ∈ [1, 20] M⊕ and a ∈ [800, 2500] au, using ATMAN v5.0 with Erebo and Solution B as fixed background bodies. Three Sednoids are tracked: 90377 Sedna, 2012 VP113, and Leleakuhonua. The sweep identifies a preferred solution at M_P3 = 12 M⊕, a_P3 = 1000 au, producing perihelion lifting ΔqSedna = +7.46 au (from 78.43 to 85.89 au) and a joint score S_joint = 0.692 — the highest in the series at the time. The control run (Erebo + Solution B only) produces Δq = −3.94 au, confirming that positive lifting requires P3. The signal is localised near a 1:3 mean-motion commensurability between P3 (P ∼ 31,600 yr) and Sedna (P ∼ 11,400 yr). The three-perturber architecture (Solution B at 75 au, Erebo at 600 au, P3 at 1000 au) partitions the outer Solar System into three independent dynamical sectors. SHA-256 (simulation output): 60c348fd1859e32f5bb45b4e155e4ef52f1f33c5ce823a83aaba536bc8553229. This is Paper VII of the ATMAN v5.0 series. Author: Ariel Fernando Martini, Buenos Aires, Argentina (2026).Contact: ariel_martini_3@hotmail.com