Double gamma-ray lines from unassociated Fermi-LAT sources revisited
  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. We conclude that the claimed high-energy
gamma-ray excess over the power-law background from unassociated sources is
nothing but an artifact of the applied selection criteria and no preference to
any excess can be claimed with the present statistics.
