Are Swift Long-Lag Gamma-Ray Bursts in the Local Supercluster?

TL;DR

This study tests whether long-lag gamma-ray bursts originate from our Local Supercluster and finds no supporting evidence, indicating they are mostly distant events rather than local ones.

Contribution

The paper provides a comprehensive analysis disproving the hypothesis that long-lag GRBs are from the Local Supercluster, clarifying their true cosmological distances.

Findings

No distribution tendency towards the Supergalactic plane

No bright host galaxies found in the Local Supercluster

Most GRBs have redshifts greater than 0.5

Abstract

A sample of 18 long-lag (tau_{lag} > 1 s) Gamma-Ray Bursts (GRBs) has been drawn from our catalog of all Swift long GRBs. Four different tests are done on this sample to test the prediction that a large fraction of long-lag GRBs are from our Local Supercluster. The results of these four tests come out that: (1) the distribution of these GRBs shows no tendency towards the Supergalactic plane; (2) the distribution shows no tendency towards the Virgo or Coma Cluster; (3) no associated bright host galaxies (m <=15) in the Local Supercluster are found for any of the 18 GRBs; (4) 17 of these 18 GRBs have redshifts of z>0.5, which are too far to be in the Local Supercluster. All these results disproved the hypothesis that any significant fraction of long-lag GRBs are from Local Supercluster. Hence these long-lag GRBs can not be counted in the calculation of LIGO detection rates. An explanation of why we can detect long-lag GRBs at high redshift is presented.