Probing the Scale of ALP Interactions with Fermi Blazars

Understand

Gamma-rays from cosmological sources contain information about gamma-ray interactions.

• Standard model and non-standard model photon interactions along the path between the source and the observer can lead to changes in the energy or state of the photons, which in turn alters the observed energy spectrum of the source.
• In general, these interactions are a function of photon energy as well as source distance.
• Here we show how existing high energy (50 GeV -- 10TeV) gamma-ray observations of blazars can be used to constrain the coupling of axion-like-particles (ALPs) to the photon.