Vol 6, No 3

Relative Spectral Lag: a New Redshift Indicator of Gamma-ray Bursts

Zhi-Bin Zhang, Jia-Gan Deng, Rui-Jing Lu, Hai-Feng Gao

Abstract

Abstract Using 64 ms count data of long gamma-ray bursts (T90>2.6 s), we analyze the quantity named relative spectral lag (RSL), τ31/FWHM(1). We investigated in detail all the correlations between the RSL and other parameters for a sample of nine long bursts, using the general cross-correlation technique that includes the lag between two different energy bands. We conclude that the distribution of RSLs is normal and has a mean value of 0.1; that the RSLs are weakly correlated with the FWHM, the asymmetry, peak flux (Fp), peak energy (Ep) and spectral indexes (α and β), while they are uncorrelated with τ31, the hardness-ratio (HR31) and the peak time (tm). Our important discovery is that redshift (z) and peak luminosity (Lp) are strongly correlated with the RSL, which can be measured easily and directly, making the RSL a good redshift and peak luminosity indicator.

Keywords

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