The Swift satellite and redshifts of long gamma-ray bursts - (Research Note)
Absztrakt:
Until 6 October 2005 sixteen redshifts had been measured of long
gamma-ray bursts discovered by the Swift satellite. Further 45
redshifts have been measured of the long gamma-ray bursts
discovered by other satellites. Here we perform five statistical
tests comparing the redshift distributions of these two samples
assuming as the null hypothesis an identical distribution for
the two samples. Three tests (Student's t-test, Mann-Whitney
test, Kolmogorov-Smirnov test) reject the null hypothesis at
significance levels between 97.19 and 98.55%. Two different
comparisons of the medians show extreme (99.78-99.99994)%
significance levels of rejection. This means that the redshifts
of the Swift sample and the redshifts of the non-Swift sample
are distributed differently - in the Swift sample the redshifts
are on average larger. This statistical result suggests that the
long GRBs should on average be at the higher redshifts of the
Swift sample.