We study correlations between various hardness ratios of gamma-ray bursts
(GRBs) and investigate if there are any differences between the two classes of
the objects in the distributions of the ratios. The results suggest that,
statistically, the slope of the higher part of the spectrum of the long
duration bursts has nothing to do with that of the lower part; emissions at
higher energy bands from the bursts of both short and long duration classes
must be significantly different for different sources, while radiations at
lower energy bands of the objects are relatively similar; the spectrum of the
short duration bursts must be harder than that of the long duration bursts,
confirming what the well-known hardness-duration correlation reveals; the
profiles of the spectra between the long duration bursts must be more similar
than that between the short duration bursts. The long duration bursts would
share more common properties than the short duration bursts. A possible
interpretation is proposed with the concept of the Doppler boosting in the
relativistic beaming model in AGNs.Comment: 38 pages, 30 figure
