相关论文: Quantitative comparisons of VHE gamma-ray blazar f…
Several models have been suggested to explain the fast gamma-ray variability observed in blazars, but its origin is still debated. One scenario is magnetic reconnection, a process that can efficiently convert magnetic energy to energy of…
The ubiquitous relativistic jet phenomena associated with black holes play a major role in high and very-high-energy (VHE) astrophysics. In particular, observations have demonstrated that blazars show VHE emission with time-variability from…
Fast $\gamma$-ray variability in blazars remains a central puzzle in high-energy astrophysics, challenging standard shock acceleration models. Blazars, a subclass of active galactic nuclei (AGN) with jets pointed close to our line of sight,…
The evolution of the spectral energy distribution during flares constrains models of particle acceleration in blazar jets. The archetypical blazar BL Lac provided a unique opportunity to study spectral variations during an extended strong…
Powerful flares from blazars with short ($\sim$ min) variability timescales are challenging for current models of blazar emission. Here, we present a physically motivated ab initio model for blazar flares based on the results of recent…
The multi-wavelength spectral and temporal variability observed in blazars set tight constraints on current theoretical emission models. Here, we investigate the relativistic magnetic reconnection process as a source of blazar emission in…
Cosmic sources of gamma-ray radiation in the GeV range are often characterized by violent variability, in particular this concerns blazars, gamma-ray bursts, and the pulsar wind nebula Crab. Such gamma-ray emission requires a very efficient…
The black hole at the center of M87 is observed to flare regularly in the very high energy (VHE) band, with photon energies $\gtrsim 100$ GeV. The rapid variability, which can be as short as $2$ days in the VHE lightcurve constrains some of…
Various attempts have been made in the literature at describing the origin and the physical mechanisms behind flaring events in blazars with radiative emission models, but detailed properties of multi-wavelength (MWL) light curves still…
Fast reconnection operating in magnetically dominated plasmas is often invoked in models for magnetar giant flares, for magnetic dissipation in pulsar winds, or to explain the gamma-ray flares observed in the Crab nebula, hence its…
Measurements from astroparticle experiments, such as the 2017 flare associated with the source TXS 0506+056, indicate that blazars act as multi-messenger (MM; radiation and neutrinos) factories. Theoretically, the particle acceleration…
Particle acceleration induced by fast magnetic reconnection may help to solve current puzzles related to the interpretation of the very high energy (VHE) and neutrino missions from AGNs and compact sources in general. Our general…
The exact mechanism for the production of fast $\gamma$-ray variability in blazars remains debated. Magnetic reconnection, in which plasmoids filled with relativistic particles and magnetic fields are formed, is a viable candidate to…
Minute-timescale TeV flares have been observed in several blazars. The fast flaring requires compact regions in the jet that boost their emission towards the observer at an extreme Doppler factor of delta>50. For TeV photons to avoid…
The mechanisms producing fast variability of the $\gamma$-ray emission in active galactic nuclei are under debate. The MAGIC telescopes detected a fast very high energy (VHE, E$>100$ GeV) $\gamma$-ray flare from BL Lacertae on 2015 June 15.…
Blazars are a subclass of active galactic nuclei (AGN) that have a relativistic jet with a small viewing angle towards the observer. Recent results based on hadronic scenarios have motivated an ongoing discussion of how a blazar can produce…
Rapid and luminous flares of non-thermal radiation observed in blazars require an efficient mechanism of energy dissipation and particle acceleration in relativistic active galactic nuclei (AGN) jets. Particle acceleration in relativistic…
We report on a multi-band variability and correlation study of the TeV blazar Mrk 421 during an exceptional flaring activity observed from 2013 April 11 to 2013 April 19. The study uses, among others, data from GASP-WEBT, Swift, NuSTAR,…
Rapid gamma-ray flares pose an astrophysical puzzle, requiring mechanisms both to accelerate energetic particles and to produce fast observed variability. These dual requirements may be satisfied by collisionless relativistic magnetic…
Order of magnitude variability has been observed in the blazar sub-class of Active Galactic Nuclei on minute timescales. These high-energy flares are often difficult to explain with shock acceleration models due to the small size of the…