Related papers: The blazar sequence revised
Blazars are a class of active galactic nuclei which host relativistic jets oriented close to the observer's line of sight. Blazars have very complex variability properties. Flares, namely flux variations around the mean value with a…
The current paradigm foresees that relativistic jets are launched as magnetically dominated flows, whose magnetic power is progressively converted to kinetic power of of the matter of the jet, until equipartition is reached. Therefore, at…
High energy emission from blazars is thought to arise in a relativistic jet launched by a supermassive black hole. The emission site must be far from the hole and the jet relativistic, in order to avoid absorption of the photons. In extreme…
Context.Blazars, a sub-category of Active Galactic Nuclei, are characterized by their non-thermal variable emission. This emission extends over the whole electromagnetic spectrum and is a consequence of particle acceleration inside their…
Being dominated by non-thermal emission from aligned relativistic jets, blazars allow us to elucidate the physics of extragalactic jets, and, ultimately, how energy is extracted from the central black hole. Crucial information about jet…
The flat spectrum radio quasars (FSRQs) are a sub-class of blazars characterised by prominent optical emission lines and a collimated large-scale jet along the observer line of sight. An X-ray spectral flattening has been reported in FSRQs…
Simultaneous observations of blazars in different spectral regimes imply that the amplitude of variability depends on the observational band. Both in the low energy spectral component and in the high energy spectral component, the amplitude…
Blazars are highly variable active galactic nuclei which emit radiation at all wavelengths from radio to gamma-rays. Polarized radiation from blazars is one key piece of evidence for synchrotron radiation at low energies and it also varies…
Many quasi-simultaneous optical observations of 17 blazars are obtained from previous papers published over the last 19 years in order to investigate the spectral slope variability and understand the radiation mechanism of blazars. The…
Blazars are a sub-category of radio-loud active galactic nuclei with relativistic jets pointing towards the observer. They exhibit non-thermal variable emission, which practically extends over the whole electromagnetic spectrum. Despite the…
In this study, we analyze the $\sim 16$ yr Fermi-LAT data of 160 blazars consisting of 92 flat-spectrum radio quasars (FSRQs), 64 BL Lacertae type objects (BL Lacs), and 4 blazar candidates of unknown type objects (BCU), and exhibit their…
The composition and energy dissipation in jets are two of the fundamental questions of jet physics that are not fully understood. In this paper, we attempt to constrain the composition, magnetization as well as radiative efficiency for…
Many of the blazars observed by Fermi actually have the peak of their time-averaged gamma-ray emission outside the $\sim$ GeV Fermi energy range, at $\sim$ MeV energies. The detailed shape of the emission spectrum around the $\sim$ MeV peak…
Blazars, a subset of powerful active galactic nuclei, feature relativistic jets that shine in a broadband electromagnetic radiation, e. g. from radio to TeV emission. Here I present the results of the studies that explore gamma-ray and…
We study the BL Lac objects detected in the one year all sky survey of the Fermi satellite, with a energy spectral slope alpha_gamma in the [0.1-100 GeV] band greater than 1.2. In the alpha_gamma vs gamma-ray luminosity plane, these BL Lacs…
We present a temporal and spectral analysis of the gamma-ray flux from nine of the brightest flat spectrum radio quasars (FSRQs) detected with the Fermi Large Area Telescope (LAT) during its first eight years of operation, with the aim of…
We use the distributions of spectral indices of a large homogenous sample of Fermi-detected blazars to re-investigate the relationship between flat spectrum radio quasars (FSRQs) and subclasses of BL Lac objects (BL Lacs). We compute the…
The Fermi-LAT survey provides a large sample of blazars selected on the strength of their inverse Compton emission. We cross-correlate the first Fermi-LAT catalogue with the CRATES radio catalogue and use this sample to investigate whether…
In recent work, we have identified two sub-populations of radio-loud AGN which appear to be distinguished by jet structure, where low-efficiency accreting systems produce `weak' jets which decelerate more rapidly than the `strong' jets of…
Blazars radiate from relativistic plasma jets with bulk Lorentz factors {\Gamma} ~ 10, closely aligned along our line of sight. In a number of blazars of the Flat Spectrum Radio Quasar type such as 3C 454.3 and 3C 279 gamma-ray flares have…