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Proceedings of IAU Symposium No. 87 held in Rome, Italy, May 8-10, 1969

An Advanced Research Workshop on Very High Energy Gamma Ray Astronomy and Related Topics was held at Durham, England during August 11-15 1986. The meeting was sponsored by the Scientific Affairs Division of NATO and the University of Durham. It is four years since the first Workshop dedicated to High Energy Gamma Ray Astronomy was held at Ootacamund, India. At that meeting the developments in Very High Energy Gamma Ray Astronomy over a period of more than 20 years were reported and the methodology, limitations, improvements and prospects for further progess were discussed. The possible requirement for a follow-up meeting was clear if the optimistic future foreseen for the field at the Ooty meeting was correct. The Durham meeting was suggested to fill this role. Although the arrangements for the Durham meeting were discussed as long ago as 1983 with possible dates in 1984 or 1986, the eventual date in 1986 has proved admirable and has coincided with a time when further advances have been reported. An important feature of the proposal for the Durham meeting was the emphasis on a series of Workshop sessions, the conclusions of each to be summarized by a Rapporteur. The purpose of these sessions was to provide a consensus view of many of the important areas in the field at a time of increasing interest by the rest of the astrophysics community.

This book contains the invited and contributed lectures presented at a meeting organised in the context of the XVIII general assembly ofthe IAU, held in Patras, August 19, 1982. Roughly one hundred scientists attended this meeting, the discussions were livel- sometimes heated - and the original time span allocated to the meeting was as a result, comfortably exceeded by about 50%. The aim of this meeting was to determine the role of galactic gamma-ray astronomy within the general concept of galactic astrophysics. The timing, at the end of the COS-B mission, was regarded as opportune, because it gives interested astrophysicists the possibility for interdisciplinary studies using the existing gamma-ray data base (e.g. comparison with infrared, radio, X-ray, etc. astronomies), as well as for theoretical studies. The next generation of gamma-ray detectors will probably not be in operation for another 5 to 10 years, and therefore it is hoped that the proceeding of this meeting can be used (in the intermediate time) as a basis for further studies, as a stimulation for more theoretical work and as an important contribution for defining the aims and operation of future gamma-ray missions. The interrelationship with other branches of astronomy, the astrophysical implications and the study of relevant physical processes using available measurements in the near-Earth environment were important results of the meeting. Many persons contributed to the success of the meeting, in particular all those who either presented a contribution and/or took part in the discussions.

Proceedings of the NATO Advanced Study Institute, Erice, Sicily, Italy, April 20-30, 1988

The `International Heidelberg Workshop on TeV Gamma-Ray Astrophysics'brought together astrophysicists from the various fields which play a role in the formation of high energy gamma-ray emission. In particular, theoretical and observational aspects of the physics and astrophysics of pulsars and quasars, the acceleration of particles at Supernova Remnants and other strong astrophysical shock fronts, and cascade processes in universal background photon fields were comprehensively discussed in more than thirty reviews by leading experts. In their entirety these reviews describe the birth of a new field of astronomy. This field concerns cosmic gamma-rays of very high energy which are observed with ground-based optical telescopes due to the Cherenkov emission of the secondary particles created by the interaction of these gamma-rays with atoms in the Earth's atmosphere. Beyond that, the workshop encompassed the latest developments and trends in theory and observation of cosmic gamma-ray sources of all energies, from nuclear gamma-ray lines in the MeV-region, through the Bremsstrahlung, Inverse Compton, and pion decay continuum emission, to gamma-rays due the decay of exotic relics from the early Universe. Audience: Specialists as well as students in physics and astrophysics and young research workers.

This volume consists of invited lectures and seminars presented at the NATO Advanced Study Institute'The Gamma Ray Sky with COMPTON GRO and SIGMA', which was held at the Centre de Physique Theorique of Les Houches (France) in January / February 1994. The school has been planned by a Scientific Organizing Committee. It was organized with the aim of providing students and young researchers with an up-to-date account of the high-energy phenomena in the vicinity of compact objets and the diffuse gamma-ray backgrounds after the early results from the gamma-ray telescope SIGMA and the four instruments onboard COMPTON GRO (Gamma Ray Observatory) : BATSE (Burst and Transient Source Experiment),COMPTEL(Compto'l Telescope),EGRET (Energetic Gamma Ray Experiment Telescope) and OS SE(Oriented Scintillation Spectrometer Experiment). It was attended by more than sixty researchers from many countries. The lectures and seminars represent a complete coverage of our present knowledge and understanding of: Gamma-ray backgrounds, Gamma-ray Burts,Active Galactic Nuclei,Galactic Compact Objects, Gamma-ray Spectroscopy, Instrumentation and observation techniques, etc... Most of these lectures are reproduced in this volume. Unfortunately, a few lecturers have chosen not to submit their manuscript.

The existence of materials with very high specific energies greatly exceeding the local virial temperature is best represented by cosmic rays, whose origin has long been a mystery. Recent astrophysical observations in X-ray, gamma-ray, neutrino, and high energy cosmic ray experiments, in conjunction with theoretical studies, have revealed various new aspects of the high energy universe, including promising candidates for cosmic ray acceleration sites. As each approach has its own advantages and limitations, it is expected that joint efforts by experimentalists and theorists in various related fields are essential.The contributions in this volume include observation of the universe through a wide range of techniques for detecting cosmic rays, neutrinos, X-rays and gamma-rays, as well as theoretical considerations in understanding their nature and astrophysical aspects.

The research program in gamma-ray astronomy focuses on increasing our knowledge of the nature and origin of galactic and extragalactic gamma rays, and understanding high-energy processes in the Sun, celestial objects, interstellar medium, and extragalactic space.This book not only provides an overview of the latest research and future plans for space-borne and ground-based experiments dedicated to the observation of the gamma-ray sky, but also addresses the topic of variable gamma-ray sources from the perspective of their identification and counterparts at different wavelengths. It further gives an overview of the theory related to the most qualified emission processes that take place in these sources and of the nature of their variability.

The contributions in this volume provide a snapshot of the latest research and future plans for space-borne and ground-based experiments dedicated to the observation of the gamma-ray sky. The articles are authored by both seasoned veterans of the first dedicated gamma-ray missions, and young scientists entering the fascinating field of gamma-ray astrophysics.With the advent of gamma-ray instrumentation on spacecraft and large and sensitive ground-based detectors, new and unexpected phenomena have been discovered, such as gamma-ray bursts and gamma-ray emission from blazars. The immense vitality of the field in the current “post-EGRET era” is witnessed by the numerous ongoing and forthcoming gamma-ray experiments documented here, complementary to various cosmic-ray, neutrino, astroparticle and X-ray projects.