Fu-Wen Zhang, Lang Shao, Jing-Zhi Yan, Da-Ming Wei
We perform a statistical analysis of the temporal and spectral properties of
the latest Fermi gamma-ray bursts (GRBs) to revisit the classification of GRBs.
We find that the bimodalities of duration and the energy ratio (Epeak/Fluence)
and the anti-correlation between spectral hardness (hardness ratio (HR), peak
energy and spectral index) and duration (\Delta T) support the
long/soft-short/hard classification scheme for Fermi GRBs. The HR - \Delta T
anti-correlation strongly depends upon the spectral shape of GRBs and energy
bands, and the bursts with the curved spectra in the typical BATSE energy bands
show a tighter anti-correlation than those with the power-law spectra in the
typical BAT energy bands. This might explain why the HR - \Delta T correlation
is not evident for those GRB samples detected by instruments with a
narrower/softer energy bandpass. We also analyze the intrinsic energy
correlation for the GRBs with measured redshift and well defined peak energies.
The current sample suggests Ep,rest=2455 \times (Eiso/10^{52})^{0.59} for short
GRBs, significantly different from that for long GRBs. However, both the long
and short GRBs comply with the same Ep,rest-Liso correlation.
View original:
http://arxiv.org/abs/1201.1549
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