Recent observations of distant gamma ray sources indicate that the universe may be more transparent to VHE-gamma-rays than expected. In this paper we study the reduction of the EBL gamma-gamma opacity due to the existence ...

The supermassive black holes in the centres of active galaxies (AGN) eject powerful relativistic jets which propagate over kpc scales, showing no significant momentum loss. Both observational evidence as well as theoretical ...

The spectral energy distributions (SEDs) and variability of astrophysical sources can be modeled in many different ways, in particular, the production of X-rays and γ-rays in the SEDs of blazars. High-energy polarimetry ...

Mildly relativistic, oblique shocks are frequently invoked as possible sites of relativistic particle acceleration and production of strongly variable, polarized multi-wavelength emission from relativistic jet sources ...

On the 28th of January, the High Energy Stereoscopic System (H.E.S.S. the world’s largest ground-based gamma-ray observatory, located in Namibia) detected an orphan TeV gamma-ray flare in 3C279, not accompanied by flaring ...

The flat spectrum radio quasar 4C +01.02 became one of the brightest active galactic nuclei detected at high redshift (z = 2.1) in gamma rays when it underwent a series of outbursts during several months in 2016. We monitored ...

The Automatic Telescope for Optical Monitoring is a 75cm optical telescope located at the H.E.S.S. site in Namibia. Since 2005, it monitors around 250 gamma-ray emitting AGN and has observed numerous blazar flares in several ...

Relativistic jets in active galactic nuclei (AGN) are among the most powerful astrophysical objects discovered to date. Indeed, jetted AGN studies have been considered a prominent science case for SKA, and were included ...

We present results of a variability study in the optical band of 44 newly identified blazar candidates behind the Magellanic Clouds. Our sample contains 27 flat spectrum radio quasars (FSRQs) and 17 BL Lacertae objects (BL ...

Jets in blazars are an excellent forum for studying acceleration at relativistic shocks using the highly-variable emission seen across the electromagnetic spectrum. Our recent work on combining multi-wavelength leptonic ...