Magnetar Giant Flares as the likely explanation of short Gamma-Ray Bursts

The origin of gamma-ray bursts, one of the most energetic events in the universe, has been a long-standing question and is still highly debated. The extremely energetic and rare giant flares from magnetars or soft gamma-repeaters (SGRs) can be thought to be one possible origin of the short gamma-ray bursts GRBs) based on their energetics. Using high energy observations of the recent GRB 200415A located close to the Sculptor galaxy, we demonstrated that the most likely explanation for the observational properties of this event,- including its location, temporal and spectral features, energy, statistical correlations, and high-energy behavior, is indeed the SGR giant flare model. The alternative compact merger falls short in reproducing the observed characteristics. This result leads a path towards probing the origin of short GRBs and shedding light on the SGR giant flare and short GRB connection.

Figure 1 shows the distribution of the observed spectral and morphological characteristics of short GRBs. The giant flare (SGR 1806-20 GF) and giant flare candidate GRBs are pointed out by the different colors and they populate distinct regions of the parameter spaces.

Figure 2 shows the spectral evolution during GRB 200415A using different thermal and non-thermal models.

Figure 1:

Figure 2:

Yang, Chand, Zhang, Yang, Zou, Yang, Zhao, Shao, Xiong, Luo, Li, Xiao, Li, Liu, Joshi, Sharma, Chakraborty, and Zhang, 2020, ApJ, 899, 106

Web link: https://iopscience.iop.org/article/10.3847/1538-4357/aba745