Extended Emission of Short Gamma-Ray Bursts

TL;DR

This paper analyzes the extended emission in short gamma-ray bursts observed with Swift/BAT, revealing a soft, flickering component lasting about 100 seconds post-trigger, which affects the classification of these bursts.

Contribution

It introduces a Bayesian blocks analysis of extended emission in short GRBs, highlighting its characteristics and potential implications for burst classification.

Findings

Extended emission lasts ~100 seconds in some short GRBs.

The extended emission is soft and flickering in nature.

Inclusion of extended emission affects GRB classification.

Abstract

Preliminary results of our analysis on the extended emission of short/medium duration GRBs observed with Swift/BAT are presented. The Bayesian blocks algorithm is used to analyze the burst durations and the temporal structure of the lightcurves in different energy bands. We show here the results of three bursts (GRBs 050724, 061006 and 070714B) that have a prominent soft extended emission component in our sample. The extended emission of these bursts is a continuous, flickering-liked component, lasting $\sim 100$ seconds post the GRB trigger at 15-25 keV bands. Without considering this component, the three bursts are classified as short GRBs, with $T_{90}=2\sim 3$ seconds. GRB 060614 has an emission component similar to the extended emission, but this component has pulse-liked structure, possibly indicating that this emission component is different from that observed in GRBs 050724, 061006, and 070714B. Further analysis on the spectral evolution behavior of the extended emission component is on going.