Related papers: PeV proton acceleration in Gamma-ray Binaries
Recently, gamma-ray emission at TeV energies has been detected from the starburst galaxies NGC253 (Acero et al., 2009) and M82 (Acciari et al., 2009. It has been claimed that pion production due to cosmic rays accelerated in supernova…
Ultrahigh-energy gamma rays ($E_{\gamma}>100 \, {\rm TeV}$) have been detected from a handful of astrophysical sources. Due to the Klein-Nishina suppression of inverse Compton scattering at such high energies, it has sometimes been argued…
Young and massive stellar clusters are a potential source of galactic cosmic rays due to at least two acceleration mechanisms. Collective stellar winds from massive stars form a wind-blown bubble with a termination shock at which particle…
Some recent experiments detecting very high energy (VHE) gamma-rays above 10-20 TeV independently reported VHE bursts for some of bright gamma-ray bursts (GRBs). If these signals are truly from GRBs, these GRBs must emit a much larger…
We argue that gamma-ray bursts (GRBs) may be the origin of the cosmic gamma-ray background radiation observed in GeV range. It has theoretically been discussed that protons may carry a much larger amount of energy than electrons in GRBs,…
We discuss the possibility of observing distant accelerators of ultra high energy cosmic rays in synchrotron gamma rays. Protons propagating away from their acceleration sites produce extremely energetic electrons during photo-pion…
The pulsar emission mechanism in the gamma-ray energy band is poorly understood. Currently, there are several models under discussion in the pulsar community. These models can be constrained by studying the collective properties of a sample…
Identifying the accelerators of Galactic cosmic ray protons (CRs) with energies up to a few PeV ($10^{15}$ eV) remains a theoretical and observational challenge. Supernova remnants (SNRs) represent strong candidates, as they provide…
The existence of a "knee" at energy ~1 PeV in the cosmic-ray spectrum suggests the presence of Galactic PeV proton accelerators called "PeVatrons". Supernova Remnant (SNR) G106.3+2.7 is a prime candidate for one of these. The recent…
We consider acceleration of leptons up to GeV-TeV energies in the bow shock wind nebula of PSR J0437-4715 and their subsequent diffusion through the interstellar magnetic fields. The leptons accelerated at the pulsar wind termination…
Protons can be plausibly accelerated to $\sim 10^{18}$-$10^{19}$ eV in strong accretion shocks surrounding massive clusters of galaxies. Such protons efficiently produce very high energy pairs through interactions with the CMB, which then…
The powerful wind-wind collision in massive star binaries creates a region of high temperature plasma and accelerates particles to relativistic energies. I briefly summarize the hydrodynamics of the wind-wind interaction and the…
We address several issues regarding the interpretation of galactic \ggg-ray sources. We consider powerful pulsars in binaries producing X-ray and gamma-ray {\it unpulsed} emission from the shock interaction of relativistic pulsar winds with…
Gamma-ray observations have established energetic isolated pulsars as outstanding particle accelerators and antimatter factories in the Galaxy. There is, however, no consensus regarding the acceleration mechanisms and the radiative…
G54.1+0.3 is a Crab-like pulsar wind nebula (PWN) with the highest $\gamma$-ray to X-ray luminosity ratio among all the nebulae driven by young rotation-powered pulsars. We model the spectral evolution of the PWN and find it difficult to…
Non-thermal particles and high-energy radiation can play a role in the dynamical processes in star-forming regions and provide an important piece of the multiwavelength observational picture of their structure and components. Powerful…
The Universe is filled with a diffuse background of MeV gamma-rays and PeV neutrinos, whose origins are unknown. Here, we propose a scenario that can account for both backgrounds simultaneously. Low-luminosity active galactic nuclei have…
Gamma-ray bursts may occur within pulsar wind bubbles (PWBs) under a number of scenarios, such as the supranova-like models in which the progenitor pulsar drives a powerful wind shocking against the ambient medium before it comes to death…
The prompt emission of gamma-ray bursts (GRBs) is widely thought to be radiation from accelerated electrons, but an appreciably larger amount of energy could be carried by accelerated protons, particularly if GRBs are the sources of…
Classical novae produce radioactive nuclei which are emitters of gamma-rays in the MeV range. Some examples are the lines at 478 and 1275 keV (from 7Be and 22Na) and the positron-electron annihilation emission, with the 511 keV line and a…