Related papers: Fast TeV variability in blazars: jets in a jet
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…
The flat spectrum radio quasar PKS 1222+216 was detected in the very high energy gamma-ray band by MAGIC during a highly active gamma-ray phase following an alert by the LAT onboard Fermi. Its relatively hard spectrum without a cut off,…
The detection of fast variations of the TeV (10^12 eV) gamma-ray flux, on time-scales of days, from the nearby radio galaxy M 87 is reported. These variations are ~10 times faster than that observed in any other waveband and imply a very…
In this work, I present a qualitative discussion on the prospect of production of ultra-high photons in blazars. The sources are a subclass of active galactic nuclei which host supermassive black holes and fire relativistic jets into the…
Relativistic outflows in the form of jets are common in many astrophysical objects. By their very nature, jets have angle dependent velocity profiles, Gamma = Gamma(r, theta, phi), where Gamma is the outflow Lorentz factor. In this work we…
A major flaring state of the BL Lac object Mrk 501 was observed by the High Energy Stereoscopic System (H.E.S.S.) in June, 2014. Flux levels higher than one Crab unit were recorded and rapid variability at very high energies ($\sim$2-20…
We construct a numerical model of emission from minijets, localized flows driven by magnetic reconnection inside Poynting-flux-dominated jets proposed to explain the ultrafast variability of blazars. The geometrical structure of the model…
We present a new time-dependent inhomogeneous jet model of non-thermal blazar emission. Ultra-relativistic leptons are injected at the base of a jet and propagate along it. We assume continuous reacceleration and cooling, producing a…
The exact location of the $\gamma$-ray emitting region in blazar jets has long been a matter of debate. However, the location has important implications about the emission processes, geometric and physical parameters of the jet, as well as…
Observations of very-high-energy (VHE, E > 250 GeV) gamma-ray emission from several blazars at z > 0.1 have placed stringent constraints on the elusive spectrum and intensity of the intergalactic infrared background radiation (IIBR).…
Blazars are known for their variability on a wide range of timescales at all wavelengths. Most studies of TeV gamma-ray blazars focus on short timescales, especially during flares. With a decade of observations from the Fermi-LAT and…
Bright and fast gamma-ray flares with hard spectra have been recently detected from the blazar 3C 279, with apparent GeV luminosities up to $10^{49}$ erg/s. The source is observed to flicker on timescales of minutes with no comparable…
TeV emission can be a common characteristic of low power blazars. This is in line with the sequence of blazars relating the observed bolometric luminosity with their overall spectral energy distribution. Detecting new TeV blazars, possibly…
Proton acceleration in nearby blazars can be diagnosed measuring their intense TeV $\gamma$-ray emission. Flux predictions for 1101+384 (Mrk421) and 1219+285 (ON231), both strong EGRET sources (0.1-10 GeV), are obtained from model spectra…
We have studied the rapid X-ray variability of three extragalactic TeV gamma-ray sources; Mrk 421, Mrk 501 and PKS 2155-304. Analyzing the X-ray light curves obtained from ASCA and/or RXTE observations between 1993 and 1998, we have…
We propose that TeV $\gamma$-ray emission from blazars is produced by collisions near the line of sight of high energy jet protons with gas targets (``clouds'') from the broad emission-line region (BLR). Intense TeV $\gamma$-ray flares…
Variability is a prominent observational feature of blazars. The high-energy radiation mechanism of jets has always been important but still unclear. In this work, we performed a detailed analysis using Fermi-LAT data across 15 years and…
We study the temporal/spectral variability of two extragalactic TeV sources, Mrk 421 and Mrk 501, based on 5-year observations with the ASCA and RXTE satellites. We found that the peak of the synchrotron emission exists just in the X-ray…
Blazars are promising sources of extragalactic high-energy astrophysical neutrinos, detected at energies $\gtrsim 10$ TeV by the IceCube neutrino observatory. Here, we report the first-ever broadband timing and spectral study of the…
(Abridged) Very high-energy (VHE, $E>100$ GeV) observations of the blazar Mrk 501 with MAGIC in 2014 provided evidence for an unusual narrow spectral feature at about 3 TeV during an extreme X-ray flaring activity. The one-zone…