The latest results on the sky distribution of ultra-high energy cosmic ray sources have consequences for their nature and time structure .
If the sources accelerate predominantly nuclei of atomic number A and charge Z and emit continuously , their luminosity in cosmic rays above \simeq 6 \times 10 ^ { 19 } eV can be no more than a fraction of \simeq 5 \times 10 ^ { -4 } Z ^ { -2 } of their total power output .
Such sources could produce a diffuse neutrino flux that gives rise to several events per year in neutrino telescopes of km ^ { 3 } size .
Continuously emitting sources should be easily visible in photons below \sim 100 GeV , but not in TeV \gamma - rays which are likely absorbed within the source .
For episodic sources that are beamed by a Lorentz factor \Gamma , the bursts or flares have to last at least \simeq 0.1 \Gamma ^ { -4 } A ^ { -4 } yr. A considerable fraction of the flare luminosity could go into highest energy cosmic rays , in which case the rate of flares per source has to be less than \simeq 5 \times 10 ^ { -3 } \Gamma ^ { 4 } A ^ { 4 } Z ^ { 2 } { yr } ^ { -1 } .
Episodic sources should have detectable variability both at GLAST and TeV energies , but neutrino fluxes may be hard to detect .