How many ultra-high energy cosmic rays could we expect from Centaurus A?

The Pierre Auger Observatory has associated a few ultra-high energy cosmic rays (UHECRs) with the direction of Centaurus A. This source has been deeply studied in radio, infrared, X-ray, and γ-rays (MeV-TeV) because it is the nearest radio-loud active galactic nucleus. Its spectral energy distribution or spectrum shows two main peaks, the low-energy peak, at an energy of 10 -2eV, and the high-energy peak, at about 150keV. There is also a faint very high energy (VHE; E ≥ 100GeV) γ-ray emission fully detected by the High Energy Stereoscopic System experiment. In this work, we describe the entire spectrum: the two main peaks with a synchrotron/synchrotron self-Compton model, and the VHE emission with a hadronic model. We consider pγ and pp interactions. For the pγ interaction, we assume that the target photons are those produced at 150keV in leptonic processes. On the other hand, for the pp interaction we consider as targets the thermal particle densities in the lobes. Requiring a satisfactory description of the spectra at very high energies with pγ interaction, we obtain an excessive luminosity in UHECRs (even exceeding the Eddington luminosity). However, when considering the pp interaction to describe the γ-spectrum, the number of UHECRs obtained is in agreement with Pierre Auger observations. We also calculate the possible neutrino signal from pp interactions on a Km3 neutrino telescope using Monte Carlo simulations. © 2012. The American Astronomical Society. All rights reserved.