Investigating Gamma-Ray Lines from Dark Matter with Future Observatories

We study the prospects for studying line features in gamma-ray spectra with upcoming gamma-ray experiments, such as HESS-II, the Cherenkov Telescope Array (CTA), and the GAMMA-400 satellite. As an example we use the narrow feature at 130 GeV seen in public data from the Fermi-LAT satellite. We found that all three experiments should be able to confidently confirm or rule out the presence of this 130 GeV feature. If it is real, it should be confirmed with a confidence level higher than 5σ. Assuming it to be a spectral signature of dark matter origin, GAMMA-400, thanks to a projected energy resolution of about 1.5 % at 100 GeV, should also be able to resolve both the γγ line and a corresponding Zγ or Hγ feature, if the corresponding branching ratio is comparable to that into two photons. It will also allow to distinguish between a gamma-ray line and the similar feature resulting from internal bremsstrahlung photons.