Related papers: New insights from cosmic gamma rays
A small number of naturally occurring, proton-rich nuclides (the p-nuclei) cannot be made in the s- and r-process. Their origin is not well understood. Massive stars can produce p-nuclei through photodisintegration of pre-existing…
Many star-forming galaxies and those hosting active galactic nuclei (AGN) show evidence of massive outflows of material in a variety of phases including ionized, neutral atomic, and molecular. Molecular outflows in particular have been the…
Galactic cosmic rays are believed to be accelerated at supernova remnant shocks. Gamma-ray observations of both supernova remnants and associated molecular clouds have been used in several occasions to test (so far quite successfully) this…
Several cosmic ray experiments have measured the positron fraction up to few hundred GeV. Their data have revealed an excess of positrons above 10 GeV that is not consistent with the secondary production of these particles in the…
The article gives a brief overview, aimed at nonspecialists, about the goals and selected recent results of the detection of very-high energy gamma-rays (energies above 100 GeV) with ground based detectors. The stress is on the physics…
The origin of the elements is a fascinating question that scientists have been trying to answer for the last seven decades. The formation of light elements in the primordial universe and heavier elements in astrophysical sources occurs…
The successful discovery of X-ray, optical and radio afterglows of gamma-ray bursts has significantly helped our understanding of these sources, and made possible the identification of host galaxies at cosmological distances. The energy…
In cosmic ray physics extensive progress has been made in recent years, both concerning theory and observation. The vast details in direct, indirect and secondary detections on the one hand provide the basis for a detailed modeling of the…
Gamma-ray bursts (GRBs) are sources of energetic, highly variable fluxes of gamma rays, which demonstrates that they are powerful particle accelerators. Besides relativistic electrons, GRBs should also accelerate high-energy hadrons, some…
The highest energy cosmic rays observed possess macroscopic energies and their origin is likely to be associated with the most energetic processes in the Universe. Their existence triggered a flurry of theoretical explanations ranging from…
It is crucial to identify the ultrahigh-energy cosmic-ray (UHECR) sources and probe their unknown properties. Recent results from the Pierre Auger Observatory favor a heavy nuclear composition for the UHECRs. Under the requirement that…
I give a brief discussion of possible sources of high energy neutrinos of astrophysical origin over the energy range from $\sim 10^{12}$ eV to $\sim 10^{25}$ eV. In particular I shall review predictions of the diffuse neutrino intensity.…
Positrons play a major role in the emission of solar gamma-rays at energies from a few hundred keV to >1 GeV. Although the processes leading to positron production in the solar atmosphere are well known, the origin of the underlying…
Massive stars form in dense and massive molecular cores. The exact formation mechanism is unclear, but it is possible that some massive stars are formed by processes similar to those that produce the low-mass stars, with accretion/ejection…
It is widely believed that multiwavelength afterglows of gamma-ray bursts (GRBs) originate from relativistic blast waves. We here show that in such blast waves, a significant fraction of the energy of shock-accelerated protons would be lost…
Air shower experiments have detected cosmic ray events of energies upto 300 EeV. Most likely these cosmic rays have originated from compact objects. Their exact sources are yet to be identified. It has been suggested before that gamma ray…
Recent observations of high ionization rates of molecular hydrogen in diffuse interstellar clouds point to a distinct low-energy cosmic-ray component. Supposing that this component is made of nuclei, two models for the origin of such…
Recent observations suggest that gamma ray bursts (GRBs) and their afterglows are produced by highly relativistic jets emitted in core collapse supernova explosions (SNe). The result of the event, probably, is not just a compact object plus…
Cosmic rays are charged relativistic particles that reach the Earth with extremely high energies, providing striking evidence of the existence of effective accelerators in the Universe. Below an energy around $\sim 10^{17}$ eV cosmic rays…
Supernova remnants are beautiful astronomical objects that are also of high scientific interest, because they provide insights into supernova explosion mechanisms, and because they are the likely sources of Galactic cosmic rays. X-ray…