SWGO is proposed as a wide-field VHE gamma-ray survey instrument with a compact inner detector array and sparser outer array, estimated at 54M USD construction cost and full operations by 2026.
Fermi-LAT Observations of Two Gamma-Ray Emission Components from the Quiescent Sun
2 Pith papers cite this work. Polarity classification is still indexing.
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We report the detection of high-energy gamma rays from the quiescent Sun with the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope (Fermi) during the first 18 months of the mission. These observations correspond to the recent period of low solar activity when the emission induced by cosmic rays is brightest. For the first time, the high statistical significance of the observations allows clear separation of the two components: the point-like emission from the solar disk due to cosmic ray cascades in the solar atmosphere, and extended emission from the inverse Compton scattering of cosmic ray electrons on solar photons in the heliosphere. The observed integral flux (>100 MeV) from the solar disk is (4.6 +/- 0.2 [statistical error] +1.0/-0.8 [systematic error]) x10^{-7} cm^{-2} s^{-1}, which is ~7 times higher than predicted by the "nominal" model of Seckel et al. (1991). In contrast, the observed integral flux (>100 MeV) of the extended emission from a region of 20 deg radius centered on the Sun, but excluding the disk itself, (6.8 +/-0.7 [stat.] +0.5/-0.4 [syst.]) x10^{-7} cm^{-2} s^{-1}, along with the observed spectrum and the angular profile, are in good agreement with the theoretical predictions for the inverse Compton emission.
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Solar axion-like particles up to 5.5 MeV produce off-axis MeV photons via two-body decay, enabling new space and terrestrial searches that could probe g_aγ down to 10^{-12} GeV^{-1}.
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The Southern Wide-Field Gamma-Ray Observatory (SWGO): A Next-Generation Ground-Based Survey Instrument for VHE Gamma-Ray Astronomy
SWGO is proposed as a wide-field VHE gamma-ray survey instrument with a compact inner detector array and sparser outer array, estimated at 54M USD construction cost and full operations by 2026.
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Looking for Lights from the Darkness: Signals from MeV-scale Solar Axion-like Particles
Solar axion-like particles up to 5.5 MeV produce off-axis MeV photons via two-body decay, enabling new space and terrestrial searches that could probe g_aγ down to 10^{-12} GeV^{-1}.