Unification of Pulses in Long and Short Gamma-Ray Bursts: Evidence from
  Pulse Properties and their Correlations
  We demonstrate that distinguishable gamma-ray burst pulses exhibit similar
behaviors as evidenced by correlations among the observable pulse properties of
duration, peak luminosity, fluence, spectral hardness, energy-dependent lag,
and asymmetry. Long and Short burst pulses exhibit these behaviors, suggesting
that a similar process is responsible for producing all GRB pulses. That these
properties correlate in the observer's frame indicates that intrinsic
correlations are strong enough to not be diluted into insignificance by the
dispersion in distances and redshift. We show how all correlated pulse
characteristics can be explained by hard-to-soft pulse evolution, and we
demonstrate that "intensity tracking" pulses not having these properties are
not single pulses; they instead appear to be composed of two or more
overlapping hard-to-soft pulses. In order to better understand pulse
characteristics, we recognize that hard-to-soft evolution provides a more
accurate definition of a pulse than its intensity variation. This realization,
coupled with the observation that pulses begin near-simultaneously across a
wide range of energies, leads us to conclude that the observed pulse emission
represents the energy decay resulting from an initial injection, and that one
simple and as yet unspecified physical mechanism is likely to be responsible
for all gamma-ray burst pulses regardless of the environment in which they form
and, if GRBs originate from different progenitors, then of the progenitors that
supply them with energy.
