Temporal Analysis of GRB Precursors in the Third Swift-BAT Catalog

TL;DR

This study analyzes the temporal properties of 52 long GRB precursors and main bursts from the Swift-BAT catalog, finding similar profiles and potential common origins, but no clear energy relation.

Contribution

It provides a systematic temporal analysis of GRB precursors, suggesting they may share the same physical origin as the main bursts, which is a novel insight.

Findings

Precursor and main burst profiles are statistically similar.

Photon counts of precursors correlate with main bursts.

No explicit energy relation between precursor and quiescent time.

Abstract

We select 52 long gamma-ray bursts(GRBs) having the precursor activity in the third Swift-BAT catalog. Each episode shown in both the precursors and the main bursts is fitted by the Norris function. We systematically analyze the temporal properties for both the precursors and the main bursts. We do not find any significant difference between the temporal profile of the precursor and that of the main burst. The photon count of the precursor is related to that of the main burst. It is indicated that the precursor and the main burst might have the same physical origin, as the precursor and the main burst follow the same $\tau_p-\omega$ relation. However, we do not find the explicit relation between the energy release of the precursor and the quiescent time. Some theoretical models, such as the fallback collapsar scenario and the jet-cocoon scenario, may be helpful to explain the GRB-precursor phenomena.