Related papers: Rapid VHE variability in blazars
The rapidly variable, very high-energy (VHE) gamma-ray emission from Active Galactic Nuclei (AGN) has been frequently associated with non-thermal processes occurring in the magnetospheres of their supermassive black holes. The present work…
The origin of extremely fast variability is one of the long-standing questions in the gamma-ray astronomy of blazars. While many models explain the slower, lower energy variability, they cannot easily account for such fast flares reaching…
Blazars, a type of active galactic nuclei (AGN) with relativistic jets pointed at the observer, exhibit flux variability across the electromagnetic spectrum due to particle acceleration in their jets. Power spectral density (PSD) studies…
Context. Blazars are a subset of active galactic nuclei (AGN) with jets that are oriented along our line of sight. Variability and spectral energy distribution (SED) studies are crucial tools for understanding the physical processes…
The observation of rapidly variable very high energy (VHE) gamma-rays from non-aligned active galactic nuclei (AGNs), as reported from M87, proves challenging for conventional theoretical acceleration and emission models. We re-examine the…
We have developed a model for the variability of gamma ray emission in jets of active galactic nuclei in which the variability arises as a result of photon-photon pair production interactions with X-rays emitted by a hot spot in the inner…
PKS 2155-304 is a blazar located in the Southern Hemisphere, monitored with the High Energy Stereoscopic System (H.E.S.S.) at very high energy (VHE, E>100 GeV) $\gamma$ rays every year since 2002. Thanks to the large data set collected in…
Variability is a general property of accretion discs and their associated jets. We introduce a semi-analytic model for particle acceleration and radio jet/lobe evolution and explore the effect of Myr timescale jet variability on the…
Critical progress in our understanding of high energy emission from AGN has been determined in the last 10 years by X-ray monitoring campaigns with many space missions, notably ROSAT, ASCA, RXTE, BeppoSAX, and XMM, often in conjunction with…
Jets associated with Active Galactic Nuclei (AGN) have been observed for almost a century, initially at optical and radio wavelengths. They are now widely accepted as "exhausts" produced electromagnetically by the central, spinning, massive…
The spectral energy distribution and variability of several blazars (Mkn 501, 1 ES 2344+51.4, PKS 2155-30.4, 1 ES 1218+30.4, 3C 454.3) along the blazar sequence is investigated using a selfconsistent and timedependent lepto-hadronic hybrid…
Among active galactic nuclei, blazars show extreme variability properties. We here investigate the case of the BL Lac object S4 0954+65 with data acquired in 2019-2020 by the Transiting Exoplanet Survey Satellite (TESS) and by the Whole…
We present the expected variability features in the context of the Synchro- Self-Compton (SSC) model of emission from Active Galactic Nuclei (AGNs) and show that the homogeneous SSC model describes well the observed multi- wavelength…
BL Lacertae (BL Lac), the archetypal blazar of its subclass and one of the most studied blazars in the last decades, has undergone a series of major multi-wavelength outbursts since 2020, resulting in its highest recorded $\gamma$-ray flare…
Radio Galaxies have by now emerged as a new $\gamma$-ray emitting source class on the extragalactic sky. Given their remarkable observed characteristics, such as unusual gamma-ray spectra or ultrafast VHE variability, they represent unique…
Large number of Active Galactic Nuclei (AGN) producing Very-High-Energy (VHE) gamma-rays (energies above 100~GeV) has been revealed using observations with Imaging Atmospheric Cherenkov Telescopes (IACTs). However, our knowledge of the VHE…
Radiation from the blazar class of of active galactic nuclei (AGN) exhibits fast time variability which is usually ascribed to instabilities in the emission region near the central supermassive black hole. The variability time scale is…
Relativistic jets are one of the most powerful manifestations of the release of energy related to the supermassive black holes at the centre of active galactic nuclei (AGN). Their emission is observed across the entire electromagnetic…
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 show variability on timescales ranging from minutes to years, the former being comparable to and in some cases even shorter than the light-crossing time of the central black hole. The observed gamma-ray lightcurves can be described…