TITLE:
Redshift Independence of the Amati and Yonetoku Relations for Gamma-Ray Bursts
AUTHORS:
Walid J. Azzam, Mohamed J. Alothman
KEYWORDS:
Gamma-Ray Bursts; Energy Correlations; Luminosity Indicators; Redshift Evolution
JOURNAL NAME:
International Journal of Astronomy and Astrophysics,
Vol.3 No.4,
October
23,
2013
ABSTRACT:
The Amati and Yonetoku relations are two of the main energy and luminosity correlations that currently exist for gamma-ray bursts (GRBs). The Amati relation is a correlation between the intrinsic peak energy, Epeak, in the vFv spectrum of a burst and its equivalent isotropic energy, Eiso. The Yonetoku relation is a correlation between Epeak and the isotropic peak luminosity, Liso. In this paper, we use a recent data sample of 65 GRBs to investigate whether these two relations evolve with redshift, z. The z-correction and thek-correction are both taken into account. Our method consists of binning the data in redshift, z, then applying (for each bin) a fit of the form:log(Eiso) = A + Blog(Epeak/Epeak>) for the Amati relation, and of the form:log(Liso) = A + Blog(Epeak/Epeak>) for the Yonetoku relation, where Epeak> is the mean value of the peak energy for the entire sample. The objective is to see whether the two fitting parameters, A and B, evolve systematically with z. Good least-squares fits were obtained with reasonable values for the linear regression coefficient, r. Our results indicate that the normalization, A, and the slope, B, do not evolve with redshift, and hence the Amati and Yonetoku relations seem to be redshift independent.