Dependence of the GRB LagLuminosity Relation on Redshift in the Source Frame
Abstract
The lagluminosity relation for gammaray bursts (GRBs) is an anticorrelation between the time lag, tau_lag, which represents the delay between the arrival of hard and soft photons, and the isotropic peak luminosity, L. In this paper, we use a sample of 43 Swift bursts to investigate whether this relation depends on redshift. Both the zcorrection and the kcorrection are taken into account. Our analysis consists of binning the data in redshift, z, then applying a fit of the form: log(L) = A + Blog(tau_lag0/<tau_lag0>) for each bin, where tau_lag0 is the timelag in the burst's source frame, and <tau_lag0> is the corresponding mean value for the entire sample. The goal is to see whether the two fitting parameters, A and B, evolve in a systematic way with z. Our results indicate that both the normalization, A, and the slope, B, seem to vary in a systematic way with redshift. We note 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. Also, the number of GRBs in the sample studied is not large, and thus our conclusions are only tentative at this point. A flat universe with omega_M = 0.27, omega_lambda = 0.73, and a Hubble constant, H_0 = 70 km s1 Mpc1 is assumed.
 Publication:

International Journal of Astronomy and Astrophysics
 Pub Date:
 2012
 DOI:
 10.4236/ijaa.2012.21001
 arXiv:
 arXiv:1203.6530
 Bibcode:
 2012IJAA....2....1A
 Keywords:

 Astrophysics  High Energy Astrophysical Phenomena
 EPrint:
 15 pages, 4 figures, 2 tables, 34 references (in press)