Pulse fitting and spectral analysis of short gamma-ray bursts and the magnetar giant flare, GRB200415A

We present pulse fitting and spectral analysis of eight short gamma-ray bursts (SGRBs) and one magnetar giant flare (MGF), GRB200415A, that were all detected by the Fermi Gamma-ray Burst Monitor and have known redshift. GRB200415A is an MGF misclassified as an SGRB because its temporal structure resembles that of SGRBs. This difficulty in distinguishing between SGRBs and MGFs hinders cosmological studies. To address this, we used pulse rise times and the power law spectral index to differentiate the two transients. Their pulses were fitted with the Norris function revealing that GRB200415A has rapid pulse rise times, while the SGRBs have slower pulse rise times. Additionally, their spectra was fitted with a power law model that has an exponential cutoff, which breaks at a few MeV for both SGRBs and the MGF. We also found that the MGF has the hardest power law index, which explains its thermal-like emission.