2025ApJ...993L...6N

We present X-ray (0.3-79 keV) and radio (0.25-203 GHz) observations of the most luminous fast blue optical transient (LFBOT) AT 2024wpp at z = 0.0868, spanning 2-280 days after first light. AT 2024wpp shows luminous (L_X ≈ 1.5 × 10⁴³ erg s^–1), variable X-ray emission with a Compton hump peaking at δt ≈ 50 days. The X-ray spectrum evolves from a soft (F_ν ∝ ν^–0.6) to an extremely hard state (F_ν ∝ ν^1.26) accompanied by a rebrightening at δt ≈ 50 days. The X-ray emission properties favor an embedded high-energy source shining through asymmetric expanding ejecta. We detect radio emission peaking at L_9 GHz_ ≈ 1.7 × 10²⁹ erg s^–1 Hz^–1 at δt ≈ 73 days. The spectral evolution is unprecedented: the early millimeter fluxes rise nearly an order of magnitude during δt ≈ 17-32 days, followed by a decline in spectral peak fluxes. We model the radio emission as synchrotron radiation from an expanding blast wave interacting with a dense environment ($\dot{M}\sim 1{0}^{-3}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ for v_w = 1000 km s^–1). The inferred outflow velocities increase from Γβc ≈ 0.07c to 0.42c during δt ≈ 32-73 days, indicating an accelerating blast wave. We interpret these observations as a shock propagating through a dense shell of radius ≈10¹⁶ cm and then accelerating into a steep density profile ρ_CSM(r) ∝ r^–3.1. All radio-bright LFBOTs exhibit similar circumstellar medium (CSM) density profiles (ρ_CSM ∝ r^–3), suggesting similar progenitor processes. The X-ray and radio properties favor a progenitor involving super-Eddington accretion onto a compact object launching mildly relativistic disk wind outflows.