(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 MP3 = 12 M⊕, aP3 = 1000 au, producing perihelion lifting ΔqSedna = +7. 46 au (from 78. 43 to 85. 89 au) and a joint score Sⱼoint = 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: arielₘartini₃@hotmail. com
Ariel Fernando Martini (Fri,) studied this question.