Related papers: Patterns of variability in gamma-ray blazars
Locating the gamma-ray emission sites in blazar jets is a long-standing and highly controversial issue. We investigate jointly several constraints on the distance scale r and Lorentz factor Gamma of the gamma-ray emitting regions in…
Context. X-ray spectral variability analyses of active galactic nuclei (AGN) with moderate luminosities and redshifts typically show a softer when brighter behaviour. Such a trend has rarely been investigated for high-luminosity AGNs ($…
Observations of very high energy gamma-rays from blazars provide information about acceleration mechanisms occurring in their innermost regions. Studies of variability in these objects allow a better understanding of the mechanisms at play.…
At the end of March 2004, the blazar S5 0716+714 underwent an optical outburst that prompted for quasi-simultaneous target-of-opportunity observations with the INTEGRAL and XMM-Newton satellites. In this paper, we report the results of the…
We report the AGILE detection and the results of the multifrequency follow-up observations of a bright $\gamma$-ray flare of the blazar 3C 279 in June 2015. We use AGILE-GRID and Fermi-LAT $\gamma$-ray data, together with Swift-XRT,…
We started a follow-up investigation of the Deep X-ray Radio Blazar Survey objects with declination >-10 deg. We undertook a survey with the EVN at 5GHz to make the first images of a complete sample of weak blazars, aiming at a comparison…
Only ~10 blazars have been detected in soft gamma-rays by OSSE and the PDS, often in flaring state. We investigate the impact of the imaging and spectral capabilities of the IBIS instrument on board INTEGRAL on the study of blazars. The…
We are presenting a detailed parameter study of the time-dependent electron injection and kinematics and the self-consistent radiation transport in jets of intermediate and low-frequency peaked BL Lac objects. Using a time-dependent,…
We present the results of our follow-up observation program of gamma-ray sources detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. 26 blazars and 39 sources unidentified at other wavelengths were…
The blazar S5 0716+714 has been monitored in its flaring state between 2015 January 19 and February 22 with Swift/XRT. During this period an exceptional flux level was observed in the X-ray range as well as in the other wavelengths, e.g.…
We present a comprehensive, two-decade, multiwavelength variability study of the blazar PKS 1510-089, one of the most prominent and extensively monitored flat-spectrum radio quasars. Using Fermi-LAT $\gamma$-ray data together with Swift-XRT…
The active galactic nucleus 4C +28.07 is a flat spectrum radio quasar, one of the brightest at $\gamma$-ray energies. We study its multi-wavelength emission by analysing $\sim12.3$ years of \textit{Fermi-LAT} data in the $\gamma$-ray band…
Blazars are active galactic nuclei with relativistic jets pointed almost directly at Earth. Blazars are characterized by strong, apparently stochastic flux variability at virtually all observed wavelengths and timescales, from minutes to…
Blazars are characterized by large amplitude and fast variability, indicating that the electron distribution is rapidly changing, often on time scales shorter than the light crossing time. We study the time dependent behavior of the…
Despite numerous studies, the origin of the gamma-ray emission from blazars is still debated, in particular whether it is produced by leptonic or hadronic processes. In this study, we are testing the leptonic scenario for the Flat Spectrum…
The blazar PKS0537-441 has been observed by Swift between the end of 2004 and November 2005. The BAT monitored it recurrently for a total of 2.7 Ms, and the XRT and UVOT pointed it on seven occasions for a total of 67 ks, making it one of…
We present the results of photometric observations of three TeV blazars, 3C 66A, S5 0954+658 and BL Lacertae, during the period 2013--2017. Our extensive observations were performed in a total of 360 nights which produced $\sim$6820 image…
We present time-resolved broad-band observations of the quasar 3C 279 obtained from multi-wavelength campaigns conducted during the first two years of the Fermi Gamma-ray Space Telescope mission. While investigating the previously reported…
The jet properties of Mrk 501 and 3C 279 are derived by fitting the broadband spectral energy distributions with the lepton models. The derived gamma_b (the break Lorenz factor of the electron distribution) are 10^4-10^6 for Mrk 501 and…
Characterisation of the long-term variations in the broad line region in a luminous blazar, where Comptonisation of broad-line emission within a relativistic jet is the standard scenario for production of gamma-ray emission that dominates…