Gamma Ray Astrophysics at Energies up to 10 GeV

Abstract

During the last two decades, gamma-ray astronomy has developed into a quantitative science, with accurate flux measurements from several sources. The Crab pulsar emits 6.17 x 10-4 E-2.2 photons cm-2 s-1 MeV-1 from 50 KeV to 5 GeV. This corresponds to about 2 x 1035 erg s-1 in each of two decades of energy. The Vela pulsar emits 3.6 x 10-4 E-1.6 photons cm-2 s-1 MeV-1 at energies 1 to 30 MeV. The luminosity of gamma rays between 10 MeV and 1 GeV is about 2 x 1034 erg/s. For the Crab nebula, the gamma ray flux is 3 x 10-3 E-2.3 photons cm-2 s-1 MeV-1 from 1 KeV to 3 GeV. The flux of the 26Al line of 1.81 MeV (if assumed to be an extended source) is (4 ± 0.4) N 10-4 photons cm-2 s-1 rad-1. The e+ annihilation line in the Galactic plane is (1.6 ± 0.3) x 10-3 photons cm-1 s-1 rad-1 on which a variable flux of < 1 x 10-3 cm-1 s-1 from the Galactic center is superimposed at certain times. Theoretical models of the sources and observations relate gamma-ray astrophysics to pulsars, neutron stars, black holes, and interstellar clouds, supernovae and supernova remnants. The processes of nucleosynthesis in supernovae and novae, and pair production near black holes yield gammaray lines. Gamma-ray observations are also related to particle acceleration processes at pulsars, neutron stars, supernova remnants, and near black holes.