Authors: Rick Leske (Caltech), J.G. Mitchell (NASA/GSFC), C.M.S. Cohen (Caltech), A.C. Cummings (Caltech), A.W. Labrador (Caltech), G.D. Muro (Caltech), M.E. Wiedenbeck (JPL/Caltech), Z. Xu ( Caltech), E.R. Christian (NASA/GSFC), G.A. de Nolfo (NASA/GSFC), D.J. McComas (Princeton University), N.A. Schwadron (Princeton, UNH)

Although primarily designed to measure charged particles, the High Energy Telescope (HET) in the ISOIS/EPI-Hi instrument on Parker Solar Probe is able to detect gamma rays as a secondary science objective. A trigger in a central region of silicon detectors with no signal in the surrounding guards or outer detectors may be produced if a gamma ray enters the region and Compton scatters or pair produces an electron. A low-level background of these “neutral” triggers is continuously present due to gamma rays produced by high-energy galactic cosmic rays interacting with material in the spacecraft or instrument, and the rate of these triggers generally increases during large solar energetic particle (SEP) events when SEP ions also generate such secondary gamma rays. However, occasionally the neutral rate shows a significant increase before the arrival of SEP particles, arising from gamma rays emitted in a gamma-ray flare rather than locally-produced secondary gammas. To date, we have uncovered 5 candidate gamma-ray flares in a preliminary survey of the neutral rate data. These events range in duration from under 1 minute to ~15 minutes, with intensities of several to ~100 times that of the quiet-time background level. We present time profiles and energy spectra of the HET gamma ray observations, describe the associated SEP events, and compare with other gamma-ray, X-ray, or EUV observations in these events where available.