The High-Magnification Channel: Why Rare Strongly Magnified Events Carry Outsized Planet Sensitivity

This paper computes why events whose peak magnification reaches hundreds, though rare, are monitored intensively: their central caustics are probed by almost every planet the lens hosts. For a representative lens of 0.3 solar masses at 4.0 kiloparsecs, in front of a source at 8.0 kiloparsecs, the angular Einstein radius is 0.553 milliarcseconds, the event timescale is 40.4 days at a relative proper motion of 5.0 milliarcseconds per year, the microlensing parallax is 0.226, and the physical Einstein radius projected at the lens is 2.21 astronomical units. The central finding is that near peak, the source passes the central caustic region regardless of planet separation, so sensitivity extends across the full separation range at reduced amplitude. All quantities are computed from stated assumptions and published survey values used as comparison points; the study is simulated and computed, not measured. Where the computation shows that an inference commonly drawn from such events is not supported at the stated precision, that negative result is reported in full.