Variation of the lagluminosity relation with redshift for Swift GRBs
Abstract
The lagluminosity relation for gammaray bursts (GRBs) is an anticorrelation between the timelag, τ _{lag}, which represents the delay between the arrival of highenergy and lowenergy photons, and the isotropic peak luminosity, L. In this paper, we investigate the possible redshift evolution of this relation by using a sample of 31 Swift bursts. Our analysis consists of binning the data in the redshift, z , then applying a fit of the form: log( L) = A + B log( τ _{lag0}/< τ _{lag0}>) for each bin, where τ _{lag0} is the timelag in the burst's rest frame, and < τ _{lag0}> is the corresponding mean value for the entire sample. The objective is to see whether the two fitting parameters, A and B , evolve in a systematic way with z. Our results indicate that the normalization, A, does seem to vary in a systematic way with redshift. The slope, B, does show some dependence on z, but this dependence is less pronounced than that of A. It should be noted, however, that although good bestfits were obtained, with reasonable values for both the linear regression coefficient, r, and the reduced chisquared, the data showed large scatter. Furthermore, the number of GRBs in the sample studied is rather small, and so our conclusions are only tentative at this point. A flat universe with Ω _{ M } = 0.27, Ω _{ Λ } = 0.73 , and a Hubble constant, H _{0} = 70 km s^{1} Mpc^{1} is assumed.
 Publication:

European Physical Journal Plus
 Pub Date:
 August 2011
 DOI:
 10.1140/epjp/i2011110740
 Bibcode:
 2011EPJP..126...74A