Identification of gamma-ray burst precursors in Fermi-GBM bursts

Abstract

We present an analysis of more than 11 years of Fermi-GBM data in which 217 gamma-ray bursts (GRBs) are found for which their main burst is preceded by a precursor flash. We find that short GRBs ($<2\text{ }\text{ }\mathrm{s}$) are $\ensuremath{\sim}10$ times less likely to produce a precursor than long GRBs. The quiescent time profile, given by the time between the precursor and the main burst, is well described by a double Gaussian distribution, indicating that the observed precursors have two distinct physical progenitors. The light curves of the identified precursor GRBs are publicly available in an online catalog (https://icecube.wisc.edu/~grbweb_public/Precursors.html).

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