Finding Fast Gamma-ray Variability in Solar Flares

Fast Radio Bursts (FRBs) are fast, bright, extragalactic transients, typically associated with magnetars. In early 2021, a very sensitive radio array observed a unique FRB-like event which localized to the Sun. This solar-FRB (sFRB) lasted for only a few milliseconds at 1.4 GHz and had a flux density of 9.1 Mega-Janskys (910 solar flux). This millisecond long sFRB was seen as a "spike" in the radio data, which raises the question, can sFRBs be detected in other wavelengths? Fermi-GBM has a 4 pi steradian field of view of the sky and measures gamma-rays down to 2 microseconds temporal resolution, which makes it the perfect instrument for detecting sFRBs. If such variability were to be found in the Fermi-GBM data, it would provide evidence that this unique energetic process spans multiple 9 orders of magnitude in energy. We performed a blind search of Solar Flares in the Fermi-GBM time-tagged event (TTE) data, binned at 10, 20, and 50 milliseconds in the 5 keV to 20 keV range starting from November 27th, 2012, and ending on April 23rd, 2021. Of the ~3500 solar flares that were examined, no statistically significant gamma-ray emission were detected. We derive upper limit density flux range for the gamma-ray emission to be 0.2 to 0.9 Janskys.