Update on Testing the Isotropy of the Properties of Gamma-Ray Bursts

TL;DR

This study applies an improved method to test the isotropy of gamma-ray burst properties across multiple catalogs, finding no significant anisotropy and confirming previous results with larger datasets.

Contribution

The paper extends and refines a method for testing GRB property isotropy, applying it to larger and additional datasets to validate previous findings.

Findings

No statistically significant anisotropy detected in GRB properties.

Results consistent with previous isotropy findings despite larger datasets.

Method remains robust across different GRB catalogs.

Abstract

Previously we proposed a novel method to inspect the isotropy of the properties of gamma-ray bursts (GRBs) such as their duration, fluences and peak fluxes at various energy bands and different time scales, complementary to existing studies of spatial distribution of GRBs by other authors. The method was then applied on the Fermi GBM Burst Catalog containing 1591 GRBs and except one particular direction where we noticed some hints of violation from statistical isotropy, the rest of the data showed consistency with isotropy. In this work we apply our method with some minor modifications to the updated Fermi/GBM data sample containing 2266 GRBs, thus $\sim 40$ % larger. We also test two other major GRB catalogs, the BATSE Current GRB Catalog of the CGRO satellite containing $\sim 2000$ bursts and the Swift/BAT Gamma-Ray Burst Catalog containing $\sim 1200$ bursts. The new results using the updated data are consistent with our previous findings and no statistically significant anisotropic feature in the observed properties of these samples of all GRBs is found.