Lower limit on isotropic energy (E_ISO) in the range 0.2–1 TeV as a function of redshift for CTA-N (α-configuration including four LSTs and nine MSTs). A short constant VHE emission of 10 s is considered, and a threshold is used on the significance (σ) of 5σ and on excess gamma-ray events (N_ex) larger than 10 to define a detection. A conservative energy threshold of E > 200 GeV (hence a slightly higher limit on ) is preferred as the observation conditions, such as weather, presence of the moon, and zenith angle dependence, impact the energy threshold. The observed spectra depending on , Γ, E_c, and redshift are shown in Fig. 3.