Space-based gamma-ray astronomy

Abstract

Gamma-ray observations give us a direct view into the most extreme environments of the universe. They help us to study astronomical particle accelerators as supernovae remnants, pulsars, active galaxies or gamma-ray bursts and help us to understand the propagation of cosmic rays through our Milky Way. This article summarizes the status of gamma-ray observations from space; it is the write-up of a rapporteur talk given at the 34 th ICRC in The Hague, The Netherlands. The primary instrument used in the presented studies is the Large Area Telescope on-board the Fermi Spacecraft, which images the whole gamma-ray sky at photon energies between 20 MeV and 2 TeV. The Fermi mission is currently in its 8 th year of observations. This article will review many of the exciting discoveries made in this time, focusing on the most recent ones.Space based gamma-ray astronomy 1 The slides of the rapporteur talk can be found under http://www.rolfbuehler.net/files/buehler_spacegamma.pdf 2 The Astro-rivelatore Gamma a Immagini Leggero (AGILE) satellite mission observing the sky at similar photon energies suffered a malfunction to the reaction wheel in November 2009, and has only been observing parts of the sky at reduced sensitivity since then. No contributions from the AGILE collaboration were submitted at the 34 th ICRC.3 http://www.slac.stanford.edu/exp/glast/groups/canda/lat_Performance.htm dN p,e,γ dE = N 0 E −Γ p,e,γ , where N 0 is a normalization factor. In cosmic-ray interactions with interstellar gas on average a fraction of the energy of the primary is transferred to gamma rays: E γ ≈ 0.1 − 0.3E p,e ). The spectral slope of the gamma-ray spectrum resulting

High-energy gamma-ray studying with GAMMA-400

“…Moreover, three catalogs of high-energy gamma-ray sources were published: 1FHL for the energy above 10 GeV [4], 2FHL for the energy range of 50 GeV -2 TeV [5], and 3FHL for the energy range of 10 GeV -2 TeV [6]. Figure 1 [7] shows the percentage of the different types of ~3030 gamma-ray sources according to the 3FGL. However, 33% of gamma-ray sources are unidentified and there no the data in the energy range of 20-100 MeV.…”

Ground-based gamma-ray astronomy

“…These 2 different strategies to detect gamma rays are very complementary: IACTs have a small field of view, a small duty cycle but very good angular and energy resolution, while particle detectors have a much larger field of view and duty cycle but poor angular resolution in comparison to the IACTs. These two types of detectors are also extremely complementary with (and benefit from) gamma-ray satellites such as Fermi-LAT which is described in an accompanying article giving a status report on space-based gamma-ray astronomy [1].…”