Understand
Context: The most nearby active galaxy Cen A has attracted considerable attention as a detected TeV gamma-ray and possible ultra-high energy (UHE) cosmic-ray emitter.
- Aims: We investigate the efficiency of particle acceleration close to the supermassive black hole (BH) horizon assuming that accretion in the innermost part of the disk occurs in an advection-dominated (ADAF) mode.
- Methods: We analyze the constraints on the achievable particle energies imposed by radiative losses and corotation for conditions inferred from observations.
- Results: We show that for an underluminous source such as Cen A, centrifugally accelerated electrons may reach Lorentz factors of up to $\gamma \sim (10^7-10^8)$, allowing inverse Compton (Thomson) upscattering of ADAF sub-mm disk photons into the TeV regime with an associated maximum (isotropic) luminosity of the order of a few times $10^{39}$ erg/s.