Double gamma-ray lines from unassociated Fermi-LAT sources revisited

Understand

We search for the presence of double gamma-ray line from unassociated Fermi-LAT sources including detailed Monte Carlo simulations to study its global statistical significance.

• Applying the Su & Finkbeiner selection criteria for high-energy photons we obtain a similar excess over the power-law background from 12 unassociated sources.
• However, the Fermi-LAT energy resolution and the present low statistics does not allow to distinguish a double peak from a single one with any meaningful statistical significance.
• We study the statistical significance of the fit to data with Monte Carlo simulations and show that the fit agrees almost perfectly with the expectations from random scan over the sky.