Gamma rays from the quasar PKS 1441+25: story of an escape

Understand

Outbursts from gamma-ray quasars provide insights on the relativistic jets of active galactic nuclei and constraints on the diffuse radiation fields that fill the Universe.

• The detection of significant emission above 100 GeV from a distant quasar would show that some of the radiated gamma rays escape pair-production interactions with low-energy photons, be it the extragalactic background light (EBL), or the radiation near the supermassive black hole lying at the jet's base.
• VERITAS detected gamma-ray emission up to 200 GeV from PKS 1441+25 (z=0.939) during April 2015, a period of high activity across all wavelengths.
• This observation of PKS 1441+25 suggests that the emission region is located thousands of Schwarzschild radii away from the black hole.