Related papers: Gamma Rays from Centaurus A
The origin of ultra-high energy (UHE) cosmic rays is still an open question. In the present work, we searched the possible UHE cosmic ray sources using the MAGIC telescope for the associated very high energy (VHE) gamma ray emission. Due to…
Recent astronomical observations reveal that Active Galactic Nuclei (AGN) are sources of high-energy radiation. For example, the Fermi-LAT and Hess telescopes have detected gamma-ray emissions from the cores of several types of AGN's. Even…
Pierre Auger experiment has detected at least a couple of ray events above energy 60 EeV from the direction of the radio-galaxy Centaurus A. Assuming those events are from Centaurus A, we have calculated the number of neutral cosmic ray…
Nearby sources of cosmic rays up to a ZeV(=10^21 eV) could be observed with a multi-messenger approach including secondary gamma-rays and neutrinos. If cosmic rays above ~10^18 eV are produced in magnetized environments such as galaxy…
The nearby radio galaxy Centaurus A is poorly studied at high frequencies with conventional radio telescopes because of its very large angular size, but is one of a very few extragalactic objects to be detected and resolved by the Wilkinson…
Different types of extragalactic objects are known to produce TeV gamma-rays. Some of these objects are the most probable candidates to accelerate cosmic rays up to 10^20 eV. It is very well known that gamma-rays can be produced as a result…
Pierre Auger observatory reported the distribution of arrival directions of the highest energy cosmic rays. These events were collected in 10 years of operations with declinations between -90$^\circ$ and +45$^\circ$. The IceCube neutrino…
As the closest known active galactic nucleus, Centaurus A (Cen A) provides a rich environment for astrophysical exploration. It has been observed across wavelengths from radio to gamma rays, and indications of ongoing particle acceleration…
The production of energetic particles in the universe remains one of the great mysteries of modern science. The mechanisms of acceleration in astrophysical sources and the details about the propagation through the galactic and extragalactic…
A detailed investigation of radio galaxies has recently stressed these sources as the possible origin of the cosmic rays observed above $3\,\text{EeV}$. Here, the relevance of this model at energies below $3\,\text{EeV}$ is investigated.…
Ultra-high-energy cosmic rays, accelerated hadrons that can exceed energies of $10^{20}$ eV, are the highest-energy particles ever observed. While the sources producing UHECRs are still unknown, the Pierre Auger Observatory has detected a…
The center of the our Galaxy is a region where very energetic phenomena take place. In particular powerful cosmic ray sources can be located in that region. The cosmic rays accelerated in these sources may interact with ambient protons…
One of the main purposes in $\gamma$-ray astronomy is linked to the origin of Galactic cosmic rays. Unlike cosmic rays, $\gamma$ rays can be used to probe their production sites in the Galaxy and to find which type of astrophysical sources…
The launch of the Fermi gamma-ray space telescope and the imaging air Cerenkov telescopes H.E.S.S., MAGIC, and VERITAS have substantially transformed our knowledge of gamma-ray sources in the last decade. The extragalactic gamma-ray sky is…
The PeV gamma ray background produced in the interactions of ultra high energy cosmic rays with the ambient matter and radiations during their propagation in the Milky Way has been calculated in this paper. If the primary ultra high energy…
The Pierre Auger observatory has presented evidence that the arrival directions of cosmic rays with energies in excess of 6x10^7 TeV may be correlated with nearby active galactic nuclei (AGN). In this context we revisit a suggestion based…
Recent X-ray and gamma-ray observations of the Galactic center region by the ASCA and CGRO/EGRET instruments show evidence of 2--10 keV and $>1$ GeV continuum emission as well as 6.7 and 6.4 keV line emission from the inner $0.2^\circ$ of…
Galaxy clusters might be sources of TeV gamma rays emitted by high-energy protons and electrons accelerated by large scale structure formation shocks, galactic winds, or active galactic nuclei. Furthermore, gamma rays may be produced in…
The question of the origin of the hard X-ray/soft gamma-ray emission in Centaurus A (Cen A) persists despite decades of observations. Results from X-ray instruments suggest a jet origin since the implied electron temperature (kT_e) would…
The diffuse $\gamma$-ray spectrum at sub-PeV energy region has been measured for the first time by the Tibet-AS$\gamma$ experiment. It will shed new light on the understanding of origin and propagation of Galactic cosmic rays at very high…