English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We study theoretical implications of a rapid very high energy (VHE) flare detected by MAGIC in the flat spectrum radio quasar PKS 1222+216. The minimum distance from the jet origin at which this flare could be produced is 0.5 pc. A moderate Doppler factor of the VHE source,D   VHE    ∼  20   , is allowed by all opacity constraints. The concurrent high‐energy (HE) emission observed by  Fermi  provides estimates of the total jet power and the jet magnetic field strength. Energetic constraints for the VHE flare are extremely tight: for an isotropic particle distribution, they require a huge comoving energy density in the emitting region and a very efficient radiative process. We disfavour hadronic processes due to their low radiative efficiency, as well as the synchrotron scenario recently proposed for the case of HE flares in the Crab nebula, since the parameters needed to overcome the radiative losses are quite extreme. The VHE emission can be explained by the synchrotron self‐Compton mechanism forD   VHE    ∼  20    or by the external radiation Compton mechanism involving the infrared radiation of the dusty torus forD   VHE    ∼  50   . After discussing several alternative scenarios, we propose that the extreme energy density constraint can be satisfied when the emission comes from highly anisotropic short‐lived bunches of particles formed by the kinetic beaming mechanism in magnetic reconnection sites. By focusing the emitting particles into very narrow beams, this mechanism allows one to relax the causality constraint on the source size, decreasing the required energy density by four orders of magnitude.

Energetic constraints on a rapid gamma‐ray flare in PKS 1222+216