Precursors of Short Gamma-Ray Bursts in the SPI-ACS/INTEGRAL Experiment

TL;DR

This study analyzed 519 short gamma-ray bursts to search for precursors, finding no significant evidence and establishing that less than 0.4% of short GRBs have precursors, based on data from multiple space observatories.

Contribution

The paper provides the first comprehensive statistical analysis of precursors in short GRBs using data from SPI-ACS/INTEGRAL and Fermi, setting upper limits on precursor occurrence.

Findings

No regular precursors detected in the averaged light curve.

Less than 0.4% of short GRBs have precursors.

Upper limits established for precursor intensity.

Abstract

We have analyzed the light curves of 519 short gamma-ray bursts (GRBs) detected in the SPI-ACS/INTEGRAL experiment from December 2002 to May 2014 to search for precursors. Both the light curves of 519 individual events and the averaged light curve of 372 brightest bursts have been analyzed. In a few cases, we have found and thoroughly studied precursor candidates based on SPI-ACS/INTEGRAL, GBM/Fermi, and LAT/Fermi data. A statistical analysis of the averaged light curve for the entire sample of short bursts has revealed no regular precursor. Upper limits for the relative intensity of precursors have been estimated. No convincing evidence for the existence of precursors of short GRBs has been found. We show that the fraction of short GRBs with precursors is less than 0.4% of all short bursts.