An observational imprint of the Collapsar model of long Gamma Ray Bursts

TL;DR

This paper presents observational evidence supporting the Collapsar model for long gamma-ray bursts, identifying a characteristic plateau in GRB duration distributions that aligns with theoretical predictions.

Contribution

It provides the first direct observational signature of the Collapsar model, linking duration distribution features to jet breakout times and suggesting many choked GRBs.

Findings

A plateau in GRB duration distribution at short timescales.

Evidence of a large population of choked (failed) GRBs.

The 2s duration cutoff is inconsistent across different satellite data.

Abstract

The Collapsar model provides a theoretical framework for the well known association between long gamma-ray bursts (GRBs) and collapsing massive stars. A bipolar relativistic jet, launched at the core of a collapsing star, drills its way through the stellar envelope and breaks out of the surface before producing the observed gamma-rays. While a wealth of observations associate GRBs with the death of massive stars, as yet there is no direct evidence for the Collapsar model itself. Here we show that a distinct signature of the Collapsar model is the appearance of a plateau in the duration distribution of the prompt GRB emission at times much shorter than the typical breakout time of the jet. This plateau is evident in the data of all three major satellites. These findings provide an evidence that directly supports the Collapsar model. Additionally, it suggests the existence of a large population of choked (failed) GRBs and that the 2 s duration commonly used to separate Collapsars and non-Collapasars is inconsistent with the duration distributions of {\it Swift} and Fermi GRBs and only holds for BATSE GRBs.