ﻻ يوجد ملخص باللغة العربية
In May - July 2014, the flat spectrum radio quasar 3C 454.3 exhibited strong flaring behaviour. Observations with the Large Area Telescope detector on-board the Fermi Gamma-ray Space Telescope captured the $gamma$-ray flux at energies 0.1 $leq E_{gamma}leq$ 300 GeV increasing fivefold during this period, with two distinct peaks in emission. The $gamma$-ray emission is analysed in detail, in order to study the emission characteristics and put constraints on the location of the emission region. We explore variability in the spectral shape of 3C 454.3, search for evidence of a spectral cutoff, quantify the significance of VHE emission and investigate whether or not an energy-dependence of the emitting electron cooling exists. $gamma$-ray intrinsic doubling timescales as small as $tau_{int} = 0.68$ $pm$ 0.01 h at a significance of > 5$sigma$ are found, providing evidence of a compact emission region. Significant $E_{gamma, emitted}geq$ 35 GeV and $E_{gamma, emitted}geq$ 50 GeV emission is also observed. The location of the emission region can be constrained to $rgeq1.3$ $times$ $R_{BLR}^{out}$, a location outside the broad-line region. The spectral variation of 3C 454.3 also suggests that these flares may be originating further downstream of the supermassive black hole than the emission before and after the flares.
We present a multi-wavelength temporal analysis of the blazar 3C 454.3 during the high $gamma$-ray active period from May-December, 2014. Except for X-rays, the period is well sampled at near-infrared (NIR)-optical by the emph{SMARTS} facility and th
The flat spectrum radio quasar 3C 279 is known to exhibit pronounced variability in the high-energy ($100,$MeV$<E<100,$GeV) $gamma$-ray band, which is continuously monitored with Fermi-LAT. During two periods of high activity in April 2014 and June 2
On 2015 June 16, Fermi-LAT observed a giant outburst from the flat spectrum radio quasar 3C 279 with a peak $>100$ MeV flux of $sim3.6times10^{-5};{rm photons};{rm cm}^{-2};{rm s}^{-1}$ averaged over orbital period intervals. It is the historically h
Context. 3C 454.3 is a very active flat spectrum radio quasar (blazar) that has undergone a recent outburst in all observed bands, including the optical. Aims. In this work we explore the short-term optical variability of 3C 454.3 during its outbur
We present multiwavelength data of the blazar 3C 454.3 obtained during an extremely bright outburst from November 2010 through January 2011. These include flux density measurements with the Herschel Space Observatory at five submillimeter-wave and fa