  The temporal properties of a sample of 498 bright gamma-ray bursts (GRBs)
with durations between 0.05 s and 674 s were analysed. The large range in
duration (T90) is accompanied by a similarly large range in the median values
of the pulse timing properties including rise time, fall time, FWHM and
separation between the pulses. Four timing diagrams relating these pulse
properties to T90 are presented and show the power law relationships between
the median values of the 4 pulse timing properties and T90, but also that the
power laws depend in a consistent manner on the number of pulses per GRB. The
timing diagrams are caused by the correlated properties of the pulses in the
burst and can be explained by a combination of factors including the Doppler
boost factor Gamma, a viewing effect caused by a jet and different progenitors.
GRBs with similar values of T90 have a wide range in the number of pulses. GRBs
with the large number of short and spectrally hard pulses may occur either from
a homogeneous jet with a higher average value of Gamma or close to the axis of
an inhomogeneous jet with higher values of Gamma near the rotation axis. The
less luminous GRBs with fewer pulses may originate further from the axis of the
inhomogeneous jet. The pulses in GRBs have six distinctive statistical
properties including correlations between time intervals, correlations between
pulse amplitudes, an anticorrelation between pulse amplitudes and time
intervals, and a link to intermittency in GRS 1915+105. The timing diagrams and
correlated pulses suggest that GRBs are powered by accretion processes
signalling jets from the formation of black holes.
