The extragalactic background light (EBL) is one of the fundamental observational quantities
in cosmology. All energy releases from resolved and unresolved extragalactic sources, and …

Ground-based γ-ray astronomy, which provides access to the TeV energy range, is a young
and rapidly develo** discipline. Recent discoveries in this waveband have important …

We describe new implementations of leptonic and hadronic models for the broadband
emission from relativistic jets in active galactic nuclei in a temporary steady state. For the …

A black hole can launch a powerful relativistic jet after it tidally disrupts a star. If this jet
fortuitously aligns with our line of sight, the overall brightness is Doppler boosted by several …

The recent Fermi observation of GRB 080916C shows that the bright photosphere emission
associated with a putative fireball is missing, which suggests that the central engine likely …

Ground-based gamma-ray astronomy has had a major breakthrough with the impressive
results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground …

Current Cherenkov telescopes have identified a population of ultra-high-frequency peaked
BL Lac objects (UHBLs), also known as extreme blazars, that exhibit exceptionally hard TeV …

We studied all blazars of known redshift detected by the Fermi satellite during its first 3-
month survey. For the majority of them, pointed Swift observations ensure a good …

Magnetic reconnection in relativistic collisionless plasmas can accelerate particles and
power high-energy emission in various astrophysical systems. Whereas most previous …

The fast TeV variability of the blazars Mrk 501 and PKS 2155− 304 implies a compact
emitting region that moves with a bulk Lorentz factor of Γem∼ 100 towards the observer …