Related papers: Hard X-ray or Gamma Ray source based on the two-st…
Many of the basic problems in the astrophysics of charged Cosmic Rays remain on principle unresolved by in situ observations in the Solar System due to the chaotic nature of the propagation of these particles in Interstellar space. This…
Despite that gamma-ray bursts is a phenomenon quite different from accreting compact objects, it could be that their hard X-ray emission is associated with a very similar mechanism of energy dissipation. In both cases, we could deal with…
We report on unusually very hard spectral states in three confirmed neutron-star low-mass X-ray binaries (1RXS J180408.9-342058, EXO 1745-248, and IGR J18245-2452) at a luminosity between ~ 10^{36-37} erg s^{-1}. When fitting the Swift…
Pulses of extreme ultraviolet (XUV) light, with wavelengths between 10 and 100$\,$nm, can be used to image and excite ultra-fast phenomena such as the motion of atomic electrons. Here we show that the illumination of plasma with…
Coalescing binary systems, consisting of two collapsed objects, are among the most promising sources of high frequency gravitational waves signals detectable, in principle, by ground-based interferometers. Binary systems of Neutron Star or…
X-ray reflection generates much of the spectral complexity in the X-ray spectra of AGN. It is argued that strong relativistic blurring of the reflection spectrum should commonly be expected from objects accreting at a high Eddington rate.…
The feasibility of gamma-ray light sources based on the channeling phenomenon of ultra-relativistic electrons and positrons in oriented single crystals is demonstrated using rigorous numerical modeling. Case studies are presented for 10 GeV…
We present a 50 ks observation of the gamma-ray binary LSI+61303 carried out with the ACIS-I array aboard the Chandra X-ray Observatory. This is the highest resolution X-ray observation of the source conducted so far. Possible evidence of…
Several cosmic ray experiments have measured excesses in electrons and positrons, relative to standard backgrounds, for energies from ~ 10 GeV - 1 TeV. These excesses could be due to new astrophysical sources, but an explanation in which…
We report the discovery of an eclipsing low-mass X-ray binary at the center of the 3FGL error ellipse of the unassociated Fermi/Large Area Telescope gamma-ray source 3FGL J0427.9-6704. Photometry from OGLE and the SMARTS 1.3-m telescope and…
ROSAT observations indicate that approximately half of all nearby groups of galaxies contain spatially extended X-ray emission. The radial extent of the X-ray emission is typically 50-500 kpc or approximately 10-50% of the virial radius of…
The hard x-ray gamma-ray absorption by cylindrically symmetric U-238 test objects is studied by means of gamma-ray transmission measurements. To make a precise comparison between the theoretically modelled values and the absorption…
Since mid-2007 we have carried out a dedicated long-term monitoring programme at 15 GHz using the Owens Valley Radio Observatory 40 meter telescope. One of the main goals of this programme is to study the relation between the radio and…
Very high energy (VHE) gamma-rays from extragalactic sources, interacting by gamma-gamma collisions with diffuse intergalactic radiation fields, provide an alternative way to constrain the diffuse background light, completely independent of…
The low energy spectra of some gamma-ray bursts' show excess components beside the power-law dependence. The consequences of such a feature allows to estimate the gamma photometric redshift of the long gamma-ray bursts in the BATSE Catalog.…
Multiwavelength radiation from relativistic particles accelerated at shocks in novae and other astrophysical sources carries a wealth of information about the outflow properties and the microphysical processes at work near the shocks. The…
Population studies of unidentified EGRET sources suggest that there exist at least three different populations of galactic gamma-ray sources. One of these populations is formed by young objects distributed along the galactic plane with a…
The X-ray, Ultraviolet, Optical emission from radio-quiet AGNs, black hole binaries, and other compact sources, in general, follow a lognormal flux distribution, a linear rms-flux relation, and a (broken) power-law power spectral densities…
Gamma-ray bursts (GRBs) are short, intense flashes of soft gamma-rays coming from the distant Universe. Long-duration GRBs (those lasting more than ~2 s) are believed to originate from the deaths of massive stars, mainly on the basis of a…
Gamma-ray bursts are still not fully understood events. However, their exploration could provide a useful tool for a better understanding of the early Universe because they belong to the most distant and violent objects that astronomers…