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 ($L_{ \rm X} \approx 1.5 \times 10^{ 43}\, \rm erg\,s^{ -1}$), variable X-ray emission with a Compton hump peaking at $\delta t \approx 50$ days. The X-ray spectrum evolves from a soft ($F_{ \nu} \propto \nu^{ -0.6}$) to an extremely hard state ($F_{ \nu} \propto \nu^{ 1.26}$) accompanied by a re-brightening at $\delta t \approx 50$\,days. The X-ray emission properties favor an embedded high-energy source shining through asymmetric expanding ejecta. We detect radio emission peaking at $L_{ \rm 9\,GHz} \approx 1.7 \times 10^{ 29}\,\rm erg\,s^{ -1}\,Hz^{ -1}$ at $\delta t \approx 73$ days. The spectral evolution is unprecedented: the early millimeter fluxes rise nearly an order of magnitude during $\delta t \approx 17-32$ 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 ($\dot{ M} \sim 10^{ -3}\, \rm M_{ \odot}\,yr^{ -1}$ for $v_{ \rm w} = 1000\,\rm km\,s^{ -1}$). The inferred outflow velocities increase from $\Gamma \beta c \approx 0.07\, \rm to\,0.42c$ during $\delta t \approx 32-73$ days, indicating an accelerating blast-wave. We interpret these observations as a shock propagating through a dense shell of radius $\approx 10^{ 16}$\,cm, then accelerating into a steep density profile $\rho_{ \rm CSM}(r) \propto r^{ -3.1}$. All radio-bright LFBOTs exhibit similar circumstellar medium (CSM) density profiles ($\rho_{ \rm CSM} \propto r^{ -3}$), 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.
Categories: astro-ph.HE