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It is commonly believed that blazar jets are relativistic magnetized plasma outflows from supermassive black holes. One key question is how the jets dissipate magnetic energy to accelerate particles and drive powerful multi-wavelength…

High Energy Astrophysical Phenomena · Physics 2022-01-26 Haocheng Zhang , Xiaocan Li , Dimitrios Giannios , Fan Guo , Hannes Thiersen , Markus Böttcher , Tiffany Lewis , Tonia Venters

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…

High Energy Astrophysical Phenomena · Physics 2018-12-04 I. M. Christie , M. Petropoulou , L. Sironi , D. Giannios

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…

High Energy Astrophysical Phenomena · Physics 2016-09-08 Krzysztof Nalewajko

Blazars are relativistic magnetized plasma outflows from supermassive black holes that point very close to our line of sight. Their emission is nonthermal dominated and highly variable across the entire electromagnetic spectrum.…

High Energy Astrophysical Phenomena · Physics 2020-10-14 Haocheng Zhang , Xiaocan Li , Dimitrios Giannios , Fan Guo , Yi-Hsin Liu , Lingyi Dong

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,…

High Energy Astrophysical Phenomena · Physics 2025-11-26 Chandan Kumar Das , Bhargav Vaidya , Amit Shukla , Giancarlo Mattia , Karl Mannheim

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…

High Energy Astrophysical Phenomena · Physics 2021-05-19 Luís H. S Kadowaki , Elisabete M. de Gouveia Dal Pino , Tania E. Medina Torrejon , Yosuke Mizuno , Pankaj Kushwaha

Blazars are characterized by relativistic jets that are closely aligned with our line of sight. This results in relativistic beaming, making blazars among the most luminous extragalactic sources across the electromagnetic spectrum, from…

High Energy Astrophysical Phenomena · Physics 2025-07-14 Stamatios Ilias Stathopoulos , Maria Petropoulou

The jet composition and energy dissipation mechanism of Gamma-ray bursts (GRBs) and Blazars are fundamental questions which remain not fully understood. One plausible model is to interpret the $\gamma$-ray emission of GRBs and optical…

High Energy Astrophysical Phenomena · Physics 2016-04-27 Wei Deng , Haocheng Zhang , Bing Zhang , Hui Li

Blazar emission models based on magnetic reconnection succeed in reproducing many observed spectral and temporal features, including the short-duration luminous flaring events. Plasmoids, a self-consistent by-product of the tearing…

High Energy Astrophysical Phenomena · Physics 2020-01-08 I. M. Christie , M. Petropoulou , L. Sironi , D. Giannios

The dissipation of energy flux in blazar jets plays a key role in the acceleration of relativistic particles. Two possibilities are commonly considered for the dissipation processes, magnetic reconnection -- possibly triggered by…

High Energy Astrophysical Phenomena · Physics 2018-06-13 F. Tavecchio , M. Landoni , L. Sironi , P. Coppi

Recently, particle in cell (PIC) simulations have shown that relativistic turbulence in collisionless plasmas can result in an equilibrium particle distribution function where turbulent heating is balanced by radiative cooling of electrons.…

High Energy Astrophysical Phenomena · Physics 2022-06-08 Zachary Davis , Jesús M. Rueda-Becerril , Dimitrios Giannios

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…

High Energy Astrophysical Phenomena · Physics 2015-05-20 Maxim V. Barkov , Felix A. Aharonian , Sergey V. Bogovalov , Stanislav R. Kelner , Dmitriy V. Khangulyan

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…

High Energy Astrophysical Phenomena · Physics 2015-06-12 Dimitrios Giannios

In this paper we investigate the properties of a sample of six BL Lacs by fitting their spectra using our inhomogeneous jet model with an accelerating, magnetically dominated, parabolic base, which transitions to a slowly decelerating…

High Energy Astrophysical Phenomena · Physics 2015-06-17 William J. Potter , Garret Cotter

We perform 3D relativistic ideal MHD simulations to study the collisions between high-$\sigma$ (Poynting-flux-dominated) blobs which contain both poloidal and toroidal magnetic field components. This is meant to mimic the interactions…

High Energy Astrophysical Phenomena · Physics 2015-06-03 Wei Deng , Hui Li , Bing Zhang , Shengtai Li

Relativistic magnetic reconnection is a powerful agent through which magnetic energy can be tapped in astrophysics, energizing particles that then produce observed radiation. In some systems, the highest energy photons come from particles…

High Energy Astrophysical Phenomena · Physics 2021-10-04 J. M. Mehlhaff , G. R. Werner , D. A. Uzdensky , M. C. Begelman

H.E.S.S. observed TeV blazar PKS 2155--304 in a strong flare state in 2006 July. The TeV flux varied on timescale as short as a few minutes, which sets strong constraints on the properties of the emission region. By use of the synchrotron…

Astrophysics · Physics 2009-11-13 M. Kusunose , F. Takahara

We present a new time-dependent inhomogeneous jet model of non-thermal blazar emission, which reproduces the entire spectral energy distribution together with the rapid gamma-ray variability. Ultra-relativistic leptons are injected at the…

Astrophysics · Physics 2011-02-11 Timothé Boutelier , Gilles Henri , Pierre-Olivier Petrucci

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…

High Energy Astrophysical Phenomena · Physics 2016-09-07 Maria Petropoulou , Dimitrios Giannios , Lorenzo Sironi

The convex (concave upward) high-energy X-ray spectra of the blazar PKS\,2155-304, observed by \emph{XMM-Newton}, is interpreted as the signature of sub-dominant inverse Compton emission. The spectra can be well fitted by a superposition of…

High Energy Astrophysical Phenomena · Physics 2021-07-21 Sitha K. Jagan , S. Sahayanathan , Frank M. Rieger , C. D. Ravikumar
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