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Register a new userGAMMA-LIGHT: High-Energy Astrophysics above 10 MeV
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High-energy phenomena in the cosmos, and in particular processes leading to the emission of gamma- rays in the energy range 10 MeV - 100 GeV, play a very special role in the understanding of our Universe. This energy range is indeed associated with non-thermal phenomena and challenging particle acceleration processes. The technology involved in detecting gamma-rays is challenging and drives our ability to develop improved instruments for a large variety of applications. GAMMA-LIGHT is a Small Mission which aims at an unprecedented advance of our knowledge in many sectors of astrophysical and Earth studies research. The Mission will open a new observational window in the low-energy gamma-ray range 10-50 MeV, and is configured to make substantial advances compared with the previous and current gamma-ray experiments (AGILE and Fermi). The improvement is based on an exquisite angular resolution achieved by GAMMA-LIGHT using state-of-the-art Silicon technology with innovative data acquisition. GAMMA-LIGHT will address all astrophysics issues left open by the current generation of instruments. In particular, the breakthrough angular resolution in the energy range 100 MeV - 1 GeV is crucial to resolve patchy and complex features of diffuse sources in the Galaxy as well as increasing the point source sensitivity. This proposal addresses scientific topics of great interest to the community, with particular emphasis on multifrequency correlation studies involving radio, optical, IR, X-ray, soft gamma-ray and TeV emission. At the end of this decade several new observatories will be operational including LOFAR, SKA, ALMA, HAWK, CTA. GAMMA-LIGHT will fill the vacuum in the 10 MeV-10 GeV band, and will provide invaluable data for the understanding of cosmic and terrestrial high-energy sources.
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Current detectors for Very-High-Energy $gamma$-ray astrophysics are either pointing instruments with a small field of view (Cherenkov telescopes), or large field-of-view instruments with relatively large energy thresholds (extensive air shower detectors). In this article, we propose a new hybrid extensive air shower detector sensitive in an energy region starting from about 100 GeV. The detector combines a small water-Cherenkov detector, able to provide a calorimetric measurement of shower particles at ground, with resistive plate chambers which contribute significantly to the accurate shower geometry reconstruction. A full simulation of this detector concept shows that it is able to reach better sensitivity than any previous gamma-ray wide field-of-view experiment in the sub-TeV energy region. It is expected to detect with a $5sigma$ significance a source fainter than the Crab Nebula in one year at $100,$GeV and, above $1,$TeV a source as faint as 10% of it. As such, this instrument is suited to detect transient phenomena making it a very powerful tool to trigger observations of variable sources and to detect transients coupled to gravitational waves and gamma-ray bursts.
In the last ten years silicon photomultipliers (SiPMs) have gained terrain in experiments and applications in which photomultiplier tubes have been the dominant photosensors during decades. Imaging Atmospheric Cherenkov Telescopes (IACTs) for very high energy (VHE, E$>$50 GeV) gamma-ray astronomy are experiencing the same process. Until now FACT was the only IACT using SiPMs. In the Cherenkov Telescope Array (CTA), the next-generation VHE gamma-ray observatory, at least 70 telescopes equipped with SiPMs are planned to be built. The first prototypes have already been constructed and are now being commissioned. Here we discuss some of the advantages and drawbacks of using SiPMs in VHE gamma-ray astronomy and provide a brief overview of different developments related to the use of SiPMs in IACTs.
Extraterrestrial gamma-ray astronomy is now a source of new knowledge in the fields of astrophysics, cosmic-ray physics, and the nature of dark matter. The next absolutely necessary step in the development of extraterrestrial high-energy gamma-ray astronomy is the improvement of the physical and technical characteristics of gamma-ray telescopes, especially the angular and energy resolutions. Such a new generation telescope will be GAMMA-400. GAMMA-400, currently developing gamma-ray telescope, together with X-ray telescope will precisely and detailed observe in the energy range of ~20 MeV to ~1000 GeV and 3-30 keV the Galactic plane, especially, Galactic Center, Fermi Bubbles, Crab, Cygnus, etc. The GAMMA- 400 will operate in the highly elliptic orbit continuously for a long time with the unprecedented angular (~0.01{deg} at E{gamma} = 100 GeV) and energy (~1% at E{gamma} = 100 GeV) resolutions better than the Fermi-LAT, as well as ground gamma-ray telescopes, by a factor of 5-10. GAMMA-400 will permit to resolve gamma rays from annihilation or decay of dark matter particles, identify many discrete sources (many of which are variable), to clarify the structure of extended sources, to specify the data on the diffuse emission.
The energy reconstruction of extensive air showers measured with the LOFAR Radboud Air Shower Array (LORA) is presented in detail. LORA is a particle detector array located in the center of the LOFAR radio telescope in the Netherlands. The aim of this work is to provide an accurate and independent energy measurement for the air showers measured through their radio signal with the LOFAR antennas. The energy reconstruction is performed using a parameterized relation between the measured shower size and the cosmic-ray energy obtained from air shower simulations. In order to illustrate the capabilities of LORA, the all-particle cosmic-ray energy spectrum has been reconstructed, assuming that cosmic rays are composed only of protons or iron nuclei in the energy range between $sim2times10^{16}$ and $2times10^{18}$ eV. The results are compatible with literature values and a changing mass composition in the transition region from a galactic to an extragalactic origin of cosmic rays.
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