RAPID TeV VARIABILITY IN BLAZARS AS A RESULT OF JET-STAR INTERACTION.

We propose a new model for the description of ultra-short flares from TeV blazars by compact magnetized condensations (blobs), produced when red giant stars cross the jet close to the central black hole. Our study includes a simple dynamic model for the evolution of the envelope lost by the star in the jet and its high-energy nonthermal emission through different leptonic and hadronic radiation mechanisms. We show that the fragmented envelope of the star can be accelerated to Lorentz factors up to 100 and effectively radiate the available energy in gamma rays predominantly through proton synchrotron radiation or external inverse Compton scattering of electrons. The model can readily explain the minute-scale TeV flares on top of longer (typical timescales of days) gamma-ray variability as observed from the blazar PKS 2155-304. In the framework of the proposed scenario, the key parameters of the source are robustly constrained. In the case of proton synchrotron origin of the emission, a mass of the central black hole of MBH 108 M⊙, a total jet power of Lj ≈ 2 x 1047 erg s-1, and a Doppler factor of the gamma-ray emitting blobs of δ ≥ 40 are required. For the external inverse Compton model, parameters of MBH ≈ 108 M⊙, Lj ≈ 1046 erg s-1, and δ ≥ 150 are required. [ABSTRACT FROM AUTHOR]