Dependence of the GRB Lag-Luminosity Relation on Redshift in the Source Frame
Abstract
The lag-luminosity relation for gamma-ray bursts (GRBs) is an anti-correlation 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 z-correction and the k-correction 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 time-lag 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 best-fits were obtained, with reasonable values for both the linear regression coefficient, r, and the reduced chi-squared, 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 s-1 Mpc-1 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
- E-Print:
- 15 pages, 4 figures, 2 tables, 34 references (in press)