Fermi Gamma-ray Space Telescope

Testing Isotropic Universe Using Properties of Gamma-Ray Bursts Detected by Fermi/GBM, CGRO/BATSE and Swift/BAT

Jakub Ripa
(Arman Shafieloo)


Previously we proposed a novel method to inspect the isotropy of the properties of GRBs such as their duration, fluences and peak fluxes at various energy bands and different time scales. 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 about 40% larger). We also test other two major GRB catalogs, the BATSE Current GRB Catalog of the CGRO satellite containing about 2000 bursts and the Swift/BAT Gamma-Ray Burst Catalog containing about 1200 bursts. The new results show proper consistency with isotropy confirming our previous findings and discarding any statistically significant anisotropic feature in the data.