z=1 Multifractality of Swift short GRBs?

TL;DR

This study uses multifractal analysis to show that short and long gamma-ray bursts have distinct angular distributions, with short GRBs exhibiting a more clustered, multifractal pattern, indicating different spatial populations.

Contribution

It demonstrates that short and long GRBs have different angular distributions, confirming the existence of two distinct spatial populations using multifractal analysis.

Findings

Long GRBs are homogeneously distributed in the sky.

Short GRBs follow a multifractal, clustered distribution.

Swift data confirms the multifractal nature of short GRBs.

Abstract

Aims. We analyze and characterize the angular distribution of selected samples of gamma ray bursts (GRBs) from Batse and Swift data to confirm that the division in two classes of short- and long-duration GRBs correspond also to the existence of two distinct spatial populations. Methods. The angular distribution is analyzed by using multifractal analysis and characterized by a multifractal spectrum of dimensions. Different spectra of dimensions indicate different angular distributions. Results. The spectra of dimensions of short and long bursts indicate that the two populations have two different angular distributions. Both Swift and BATSE long bursts appear to be homo- geneously distributed in the sky with a monofractal distribution. Short GRBs follow instead a multifractal distribution for both the two samples. Even if BATSE data may not give a secure in- terpretation of their angular distribution because of the instrumental selection effects that mainly favor the detection of near GRBs, the results from Swift short GRBs confirm this behavior, also when are included GRBs corrected by the redshift factor. The distributions traced by short GRBs, up to z = 1, depict a universe with a structure similar to that of a disordered porous material with uniformly distributed heterogeneous irregular structures, appearing more clustered than what expected.