A Precessing, Magnetically Dominated, Structured Jet Powering the Hour-scale Quasiperiodic GRB 250702B

Abstract GRB 250702B shows ultralong episodic prompt activity (three hard-gamma-ray episodes over ≃3.2 hr with quasi-regular spacing P ≃ 2825 s) preceded by a soft-X-ray flare about one day earlier. We interpret these phenomena with a unified scenario in which a stellar-mass black hole accretes from a massive misaligned debris disk and launches a magnetically dominated, precessing, structured (spine–sheath) jet. The engine “clock” arises from Lense–Thirring precession of the outer annulus of a geometrically thick inner torus at r ≈ 250–300 r g , while the hard spectra reflect magnetic reconnection dissipation in the spine. A slightly off-axis viewing geometry resolves the apparent opening-angle tension without invoking late energy injection. “Missing” pulses in the second/third cycles occur naturally when low-amplitude nutation causes the beaming cone to miss the line of sight. The model yields concrete, falsifiable predictions, providing a self-consistent explanation of GRB 250702B’s radiative and outflow anomalies.