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Long high redshift GRB and XRT/SWIFT lightcurves

Analysis of long SWIFT GRB ($t_{90}>2~s$)redshift distribution have shown that confidence level of single peak approximation of this distribution is only $\sim70\%$ and more than 30\% GRB are in very heavy tails outside $3\sigma$ level for this fit. But less than 9\% events are outside $3\sigma$ level for really uniform sources sets in our Metagalaxy (as examples SNIa and first 604 QSO from 2QZ\_6QZ catalogue were analyzed). More detailed analysis of long GRB redshift distribution reveal that at 97\% confidence level three subgroups could be separated with following parameters: $<z_1>=0.9 \pm 0.1$, $<z_2>=2.4 \pm 0.3$ and $<z_3>=3.4 \pm 0.4$. The XRT/SWIFT lightcurves for these groups of GRB were considered and it have shown that distributions of ratio of XRT 24 hour flux to XRT early flux for second group more restricted than for third group. Moreover, at least 90\% XRT/SWIFT lightcurves for GRB with z>3 are more complicated and have some maxima. It allows us to make conclusion that SWIFT long GRB sources subset is not uniform.

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