GAMMA-RAY FLARES FROM RED GIANT/JET INTERACTIONS IN ACTIVE GALACTIC NUCLEI

Non-blazar active galactic nuclei (AGNs) have been recently established as a class of gamma-ray sources. M87, a nearby representative of this class, shows fast TeV variability on timescales of a few days. We suggest a scenario of flare gamma-ray emission in non-blazar AGNs based on a red giant (RG) interacting with the jet at the base. We solve the hydrodynamical equations that describe the evolution of the envelope of an RG blown by the impact of the jet. If the RG is at least slightly tidally disrupted by the supermassive black hole, enough stellar material will be blown by the jet, expanding quickly until a significant part of the jet is shocked. This process can render suitable conditions for energy dissipation and proton acceleration, which could explain the detected day-scale TeV flares from M87 via proton-proton collisions. Since the radiation produced would be unbeamed, such an event should be mostly detected from non-blazar AGNs. They may be frequent phenomena, detectable in the GeV-TeV range even up to distances of similar to 1 Gpc for the most powerful jets. The counterparts at lower energies are expected to be not too bright. M87, and nearby non-blazar AGNs in general, can be fast variable sources of gamma-rays through RG/jet interactions.