MeV-GeV Gamma-Ray Astrophysics in the Multimessenger Era
A comprehensive review examines gamma-ray astrophysics across nine orders of magnitude in photon energy, from pioneering 1950s predictions to modern multimessenger astronomy. The field has matured significantly but faces a critical sensitivity gap in the MeV energy range that limits understanding of nucleosynthesis, dark matter, and transient phenomena. Closing this "MeV gap" is essential for advancing multimessenger astronomy and understanding the universe's most extreme particle accelerators.
This arXiv physics paper surveys the scientific foundations and historical development of gamma-ray astrophysics, tracing the field from theoretical predictions in the 1950s through first space-borne detections in the 1960s to contemporary observations spanning nine orders of magnitude in photon energy up to PeV scales. The review identifies a critical observational limitation: the "MeV gap" between a few hundred keV and a few GeV, where current instruments lack sufficient sensitivity. This gap constrains progress on multiple fronts, including nucleosynthesis mechanisms, positron annihilation physics, transient phenomena, dark-matter detection signatures, and the identification of electromagnetic counterparts to high-energy neutrinos and gravitational waves. The paper discusses programmatic efforts to address this sensitivity limitation and emphasizes how gamma-ray astronomy naturally interfaces with the emerging multimessenger framework that combines photons, neutrinos, and gravitational waves.
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MeV-GeV Gamma-Ray Astrophysics in the Multimessenger Era
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