Factor analysis of the long gamma-ray bursts

Abstract

Aims. We study statistically 197 long gamma-ray bursts, detected and measured in detail by the BATSE instrument of the Compton Gamma-Ray Observatory. In the sample, 10 variables, describing for any burst the time behavior of the spectra and other quantities, are collected.Methods. The factor analysis method is used to find the latent random variables describing the temporal and spectral properties of GRBs.Results. The application of this particular method to this sample indicates that five factors and the REpk spectral variable (the ratio of peak energies in the spectrum) describe the sample satisfactorily. Both the pseudo-redshifts inferred from the variability, and the Amati-relation in its original form, are disfavored. © 2008 ESO.