Extending Fermi-LAT and H.E.S.S. Limits on Gamma-ray Lines from Dark Matter Annihilation

Understand

Gamma-ray lines from dark matter annihilation ($\chi\chi\to \gamma X$, where $X=\gamma,h,Z$) are always accompanied, at lower energies, by a continuum gamma-ray spectrum stemming both from radiative corrections ($X=\gamma$) and from the decay debris of the second particle possibly present in the final state ($X=h,Z$).

• This model-independent gamma-ray emission can be exploited to derive novel limits on gamma-ray lines that do not rely on the line-feature.
• Although such limits are not expected to be as stringent, they can be used to probe the existence of $\gamma$-ray lines for dark matter masses beyond the largest energies accessible to current telescopes.
• Here, we use continuous gamma-ray searches from Fermi-LAT observations of Milky Way dwarf spheroidal galaxies and from H.E.S.S.