Related papers: High-energy gamma-rays from stellar associations
A part of early type stars is characterised by strong dipole magnetic field that is modified by the outflow of dense wind from the stellar surface. At some distance from the surface (above the Alfven radius), the wind drives the magnetic…
Star-forming galaxies are huge reservoirs of cosmic rays (CRs) and these CRs convert a significant fraction of their energy into $\gamma$-rays by colliding with the interstellar medium (ISM). Several nearby star-forming galaxies have been…
Gamma Ray Bursts (GRBs) have been proposed as one {\it possible} class of sources of the Ultrahigh Energy Cosmic Ray (UHECR) events observed up to energies $\gsim10^{20}\ev$. The synchrotron radiation of the highest energy protons…
Ultra-high-energy cosmic rays (UHECRs) have been tried to be related to the most varied and powerful sources known in the universe. Gamma-ray bursts (GRBs) are natural candidates. Here, we argue that cosmic rays can be accelerated by large…
We propose that TeV $\gamma$-ray emission from blazars is produced by collisions near the line of sight of high energy jet protons with gas targets (``clouds'') from the broad emission-line region (BLR). Intense TeV $\gamma$-ray flares…
A fraction of core collapse supernovae of type Ib/c are associated with Gamma-ray bursts, which are thought to produce highly relativistic jets. Recently, it has been hypothesized that a larger fraction of core collapse supernovae produce…
Astrophysical neutrinos can be produced in proton interactions of charged cosmic rays with ambient photon or baryonic fields. Cosmic rays are observed in balloon, satellite and air shower experiments every day, from below 1e9 eV up to…
Very-high energy (GeV-TeV) gamma rays in the universe suggest the presence of an accelerator in the source. Neutrinos and gamma rays are intriguing astrophysical messengers. Multi-messenger particle emission produced by interactions of…
Powerful winds with wide opening angles, likely driven by accretion disks around black holes (BHs), are observed in the majority of active galactic nuclei (AGN) and can play a crucial role in AGN and galaxy evolution. If protons are…
The development of techniques whereby gamma rays of energy 100 GeV and above can be studied from the ground, using indirect, but sensitive, techniques has opened up a new area of high energy photon astronomy. The most exciting result that…
The impact of non-thermal processes on the spectral energy distributions of galaxies can be dramatic, but such processes are often neglected in considerations of their structure and evolution. Particle acceleration associated with high mass…
Using the cosmic ray (CR) data available in the energy interval $(10 - 2 \times 10^{7})$ GeV/particle, we have calculated the profile of the primary $\gamma$-ray spectrum produced by the interaction of these CR with thermal nuclei of the…
Supernova remnants (SNRs) have long been hypothesized as the main source of Galactic Cosmic Rays up to PeV energies. Some of them have indeed been shown to accelerate protons to TeV energies and above. But which of them are indeed efficient…
The propagation of gamma-rays over cosmological distances is the subject of extensive theoretical and observational research at GeV and TeV energies. The mean free path of gamma-rays in the cosmic web is limited above 100 GeV due to the…
If cosmic rays with energies <100 TeV originate in the galaxy and are accelerated in shock waves in shell-type supernova remnants (SNRs), gamma-rays will be produced as the result of proton and electron interactions with the local…
We propose a new hypothesis for the origin of the major part of non-solar hadronic cosmic rays (CRs) at all energies: highly relativistic, narrowly collimated jets from the birth or collapse of neutron stars (NSs) in our Galaxy accelerate…
Gamma-Ray Bursts (GRBs) are expected to efficiently accelerate protons up to relativistic energies. High-energy photons can originate from decay of neutral pions produced by the interaction of these protons with the medium surrounding the…
Massive protostars have associated bipolar outflows with velocities of hundreds of km s$^{-1}$. Such outflows can produce strong shocks when interact with the ambient medium leading to regions of non-thermal radio emission. We aim at…
We explore scenarios where the highest energy cosmic rays (HECR) are produced by new particle physics near the grand unification scale. Using detailed numerical simulations of extragalactic cosmic and gamma-ray propagation, we show the…
The distribution of cosmic rays in the Galaxy at energies above few TeVs is still uncertain and this affects the expectations for the diffuse gamma flux produced by hadronic interactions of cosmic rays with the interstellar gas. We show…