1209.4647 (Amir Shahmoradi)
Amir Shahmoradi
It is proposed that the luminosity function, the comoving-frame spectral correlations and distributions of cosmological Long-duration Gamma-Ray Bursts (LGRBs) may be very well described as multivariate log-normal distribution. This result is based on careful selection, analysis and modeling of the spectral parameters of LGRBs in the largest catalog of Gamma-Ray Bursts available to date: 2130 BATSE GRBs, while taking into account the detection threshold and possible selection effects on observational data. Constraints on the joint quadru-variate distribution of the isotropic peak luminosity, the total isotropic emission, the comoving-frame time-integrated spectral peak energy and the comoving-frame duration of LGRBs are derived. Extensive goodness-of-fit tests are performed. The presented analysis provides evidence for a relatively large fraction of LGRBs that have been missed by BATSE detector with total isotropic emissions extending down to 10^49 [erg] and observed spectral peak energies as low as 5 [KeV]. The model predicts a fairly strong but significant correlation (Pearson's \rho=0.58\pm0.04 at >14\sigma) for the Amati relation and a moderate correlation for the Yonetoku relation. The strength and significance of the correlations found, encourage the search for the underlying mechanisms, though undermines their capabilities as probes of Dark Energy's equation of state at high redshifts. Corroborating recent reports on the apparent observed flattening in the Number-Intensity distribution (log(N)-log(P) diagram) of LGRBs, the model further extends the reported flattening to a turnover at the bolometric 1-second peak energy flux Pbol~5*10^(-8) [erg/s/cm^2]. The presented analysis favors - but does not necessitate - a cosmic rate for BATSE LGRBs tracing the metallicity evolution consistent with a cutoff ~0.2-0.5, assuming no luminosity-redshift evolution.
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http://arxiv.org/abs/1209.4647
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