Uses the Fermi-LAT-detected 2022-2023 gamma-ray outburst of 3C 216 -- a compact steep spectrum (CSS) radiogalaxy rather than a closely jet-aligned blazar -- together with coordinated Swift X-ray, UV and optical data to show that the flaring multifrequency spectral energy distribution evolves coherently and is well reproduced by a single emission zone dominated by synchrotron self-Compton emission. The novel contribution is demonstrating that a low-free-parameter single-zone SSC model accounts for high-energy emission even in a CSS source, extending SSC diagnostics of AGN jet emitting regions beyond the usual blazar geometry.
Reports the first Fermi-LAT detection of a gamma-ray outburst from 3C 216, an extragalactic compact steep spectrum (CSS) radiogalaxy associated with 4FGL J0910.0+4257. Beginning in November 2022, Fer…