Abstract
The detection of GW170817, it's extensive multi-wavelength follow-up campaign, and the large amount of theoretical development and interpretation that followed, have resulted in a significant step forward in the understanding of the binary neutron star merger phenomenon as a whole. One of its aspects is seeing the merger as a progenitor of short gamma-ray bursts (SGRB), which will be the subject of this review. On the one hand, GW170817 observations have confirmed some theoretical expectations, exemplified by the confirmation that binary neutron star mergers are the progenitors of SGRBs. In addition, the multimessenger nature of GW170817 has allowed for gathering of unprecedented data, such as the trigger time of the merger, the delay with which the gamma-ray photons were detected, and the brightening afterglow of an off-axis event. All together, the incomparable richness of the data from GW170817 has allowed us to paint a fairly detailed picture of at least one SGRB. I will detail what we learned, what new questions have arisen, and the perspectives for answering them when a sample of GW170817-comparable events have been studied.
Highlights
Gamma-ray bursts (GRBs) are some of the most energetic explosions in the present day Universe, characterized by the release of large amounts of energy, within a few milliseconds to tens of seconds, resulting in the acceleration of relativistic outflows and the release of high-energy photons (Fishman and Meegan, 1995; Piran, 1999; Mészáros, 2002; Gehrels et al, 2009; Kumar and Zhang, 2015)
GW170817 was a rich event, a cornerstone detection in our understanding of SGRBs. It confirmed that binary NS mergers are the progenitor of at least some short bursts, it showed us that the top-hat jet model is woefully inadequate for describing the relativistic outflows of SGRBs and it gave us, for the first time ever, a measure of the trigger time and of the delay between the launching of the jet and the detection of the prompt emission radiation
We know that the burst associated with GW170817 was a fairly canonical SGRB (Salafia et al., 2019), with a powerful relativistic jet that, after interacting with the merger wind, turned into a structured outflow (Lazzati et al., 2017b; Lazzati et al., 2018)
Summary
Gamma-ray bursts (GRBs) are some of the most energetic explosions in the present day Universe, characterized by the release of large amounts of energy, within a few milliseconds to tens of seconds, resulting in the acceleration of relativistic outflows and the release of high-energy photons (Fishman and Meegan, 1995; Piran, 1999; Mészáros, 2002; Gehrels et al, 2009; Kumar and Zhang, 2015) They can be divided in at least two classes, based on the duration of their prompt phase, in which their emission is concentrated in the hard X-ray and gamma-ray bands and is characterized by fast variability (Kouveliotou et al, 1993). In this contribution I will review the key observations of GW170817 as a SGRB ( known as GRB170817A), the questions that were answered, and the new ones that were spurred, and briefly discuss what more insight is expected from the detection of more systems akin to GW170817 in future GW observing runs
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