R. Ruffini,1,2,3 M.G. Bernardini,1,2 C.L. Bianco,1,2,3 L. Caito,1,2 P. Chardonnet,1,3,4 C. Cherubini,1,5 M.G. Dainotti,1,2 F. Fraschetti, A. Geralico,1,2 R. Guida,1,2 B. Patricelli,1,2 M. Rotondo,1,2 J.A. Rueda Hernandez,1,2 G. Vereshchagin,1,2,3 S.-S. Xue1,3 1 ICRANet and ICRA, Piazzale della Repubblica 10, I-65122 Pescara, Italy. 2 Dip. di Fisica, Università di Roma “La Sapienza”, Piazzale Al...

Roughly 60 blazars have been identiied with > 100 MeV EGRET gamma-ray sources, and exhibit inferred isotropic luminosities as large as 3 10 49 ergs s ?1. The two most remarkable characteristics about the EGRET observations are that the-ray luminosity often dominates the bolometric power, and that variability on timescales at least as short as a day is seen from several sources in their aring st...

Pulsars are among the most exciting gamma ray sources in the Universe and can serve as unique sites for the study of emission processes in extreme physical environments. The Gamma ray Large Area Space Telescope (GLAST) will increase dramatically our knowledge of gamma ray pulsars physics. In particular the Large Area Telescope (LAT), the main GLAST instrument, will provide more detailed observa...

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The six or more pulsars seen by CGRO/EGRET show that: the light curves usually have double-peak structures (suggesting a broad cone of emission); gamma rays are frequently the dominant component of the radiated power; and all the spectra show evidence of a high...

We estimate the fraction of the total energy in a Gamma-Ray Burst (GRB) that is radiated in photons during the main burst. Random internal collisions among different shells limit the efficiency for converting bulk kinetic energy to photons. About 6% of the energy of explosion is converted to radiation for long duration bursts (lasting 10s or more); the efficiency is significantly smaller for sh...

Gamma ray sources with high flux and spectral densities are the main requirements for new nuclear physics experiments to be performed in several worldwide laboratories with dedicated facilities. The paper is focalized on a proposal of experiment on γ photons production using Compton collisions between the DAΦNE electron beam and a high average power laser pulse, amplified in a Fabry-Pérot optic...

1. Abstract GRBs have remained a puzzle for many high–energy astrophysicists since their discovery in 1967. With the advent of the X–ray satellites BeppoSAX and RossiXTE, it has been possible to carry out deep multi-wavelength observations of the counterparts associated with the GRBs just within a few hours of occurence, thanks to the observation of the fading X-ray emission that follows the mo...

An astrophysics application of a low noise Double-sided Silicon Strip Detector (DSSD) is described. A Semiconductor Multiple-Compton Telescope (SMCT) is being developed to explore the gamma-ray universe in the 0.1– 20 MeV energy band. Excellent energy resolution and polarization sensitivity are key features of the SMCT. We have developed prototype modules for a low noise DSSD system, which reac...

The evidence for spectral features in gamma-ray bursts is summarized. As a guide for evaluating the evidence, the properties of gamma-ray detectors and the methods of analyzing gamma-ray spectra are reviewed. In the 1980’s, observations indicated that absorption features below 100 keV were present in a large fraction of bright gamma-ray bursts. There were also reports of emission features aroun...