Particle acceleration in Ultra Fast Outflows

Ultra-fast outflows (UFOs) – midly relativistic wide-opening angle winds from active galactic nuclei–haverecentlybeenidentifiedthroughX-rayspectroscopyandmaycontributetotheorigin ofhigh-energycosmicrays. Throughdiffusiveshockacceleration(DSA)atstrongsub-relativistic shocks,UFOscanaccelerateparticlesuptoveryhighenergies(VHE)andevenultra-highenergies (UHE).Interactionsoftheseparticleswiththesurroundingdensemediumareexpectedtoproduce gamma rays andneutrinos. WemodelparticleaccelerationinUFO-drivenshocksusingDSAandestimatetheresultinghigh- energy gamma-ray and neutrino fluxes. We develop a semi-analytical model to predict these emissions andassesstheir detectabilitywith current andfuture observatories. Our preliminary results suggest that some UFOs – particularly nearby ones with high wind velocities (up to 0.4 c) – could be detectable at very high energies. In particular, if the spectrum of accelerated particles is sufficiently hard and the acceleration efficiency is high, some UFOs couldproduceadetectableVHEgamma-rayfluxwhileremainingundetectedintheGeVbandby Fermi-LAT. As a next step, we aim to identify the most promising UFO candidates for detection in the TeV range, with a focus on the CTAO and LHAASO for gamma rays, and IceCube for neutrinos. We also investigate therelativecontributions ofhadronic andleptonic emission scenarios.