Red-Shift Distribution of Gamma-ray Bursts and Their Progenitors

TL;DR

This paper analyzes the red-shift distribution of gamma-ray burst subclasses to infer their progenitors, finding distinct distributions that suggest different origins for the subclasses of long-soft gamma-ray bursts.

Contribution

It extends the analysis of red-shift distributions to possible subclasses of long-soft gamma-ray bursts, revealing differences that help constrain their progenitor models.

Findings

Two subclasses of L-GRBs have different red-shift distributions.

Red-shift distribution differences are prominent for z > 1.

Red-shift distribution can be used to infer progenitor characteristics.

Abstract

Gamma ray bursts have been divided into two classes, long-soft gamma ray burst and short-hard gamma ray burst according to the bimodal distribution in duration time. Due to the harder spectrum and the lack of afterglows of short-hard bursts in optical and radio observations, different progenitors for short-hard bursts and long-soft bursts have been suggested. Based on the X-ray afterglow observation and the cumulative red-shift distribution of short-hard bursts, Nakar et al. (2006) found that the progenitors of short-hard bursts are consistent with old populations, such as mergers of binary neutron stars. Recently, the existence of two subclasses in long-soft bursts has been suggested after considering multiple characteristics of gamma-ray bursts, including fluences and the duration time. In this work, we extended the analysis of cumulative red-shift distribution to two possible subclasses in L-GRBs. We found that two possible subclass GRBs show different red-shift distributions, especially for red-shifts z > 1. Our results indicate that the accumulative red-shift distribution can be used as a tool to constrain the progenitor characteristics of possible subclasses in L-GRBs.