The signature of an anisotropic distribution of gamma-ray bursts

Lixiong Gan, Yuan-Chuan Zou, Zi-Gao Dai

Published 2014-06-27Version 1

Anomalies of the cosmic microwave background (CMB) maps have been widely acquainted nowadays from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite to the Planck satellite. One of the anomalies is a multipole alignment from $l=2$ to $l=5$. In our work, we investigate the angular distribution of gamma-ray bursts (GRBs) to find whether there is the same anomaly of GRB as CMB. We perform spherical harmonics expansion on GRB samples to derive coefficients of a few first terms of the expansion terms and find that there is rough multipole alignment from $l=2$ to $l=4$ while the dipole and $l=5$ multipole is in a distant direction, and that the quadrupole is obviously planar and the other ones are normal.