Overview
- New papers published July 14, 2026, present AT2019ijn as a fast, blue optical flare in the nucleus of a dwarf galaxy at z = 0.273 that rose to peak brightness in about five to seven days and stayed hot as it faded.
- Radio emission emerged much later, peaking roughly 640 days after the optical flash with a peak luminosity near 2×10^31 erg s^-1 Hz^-1 and an implied energy of order 2×10^52 erg, and the radio afterglow persisted for more than six years.
- Broadband modeling by the authors favors a relativistic jet seen off axis at about a 40° viewing angle, which explains the delayed, very bright radio peak while producing little prompt high‑energy emission.
- The teams favor a jetted tidal disruption event by an intermediate‑mass black hole (about 10^4–10^6 solar masses, best fits near 10^5 M☉) as the most likely engine, but they state alternatives such as a jetted magnetar or exotic merger cannot be fully excluded.
- The papers say AT2019ijn points to a new class of radio‑loud optical transients and recommend wide radio surveys and long‑term follow up as the best way to find more off‑axis jetted events and to probe elusive intermediate‑mass black holes.