The analysis of gamma-ray burst (GRB) spectra often relies on empirical
models like the Band function, which lacks a distinct physical explanation.
Previous attempts to couple physical models with observed data have been
confined to individual burst studies, where the model is fitted to segmented
spectra with independent physical parameters. These approaches frequently fail
to explain the spectral evolution, which should be governed by a consistent set
of physical conditions. In this study, we propose a novel approach by
incorporating the synchrotron radiation model to provide a self-consistent
explanation for a selection of single-pulse GRBs. Our sample is carefully
chosen to minimize contamination from overlapping pulses, allowing for a
comprehensive test of the synchrotron model under a unified physical condition,
such as a single injection event of electrons. By tracing the evolution of
cooling electrons in a decaying magnetic field, our model predicts a series of
time-dependent observed spectra that align well with the observed data.
Remarkably, using a single set of physical parameters, our model successfully
fits all time-resolved spectra within each burst. Additionally, our model
accurately predicts the evolution of some key features of GRBs such as the
spectral peak Ep​ and light curve shapes, all of which are consistent
with observations. Our findings strongly support the notion that the spectral
and temporal evolution in GRB pulses originates from the expansion of the GRB
emission region with an initial radius of approximately 1015 cm, with
synchrotron radiation being the underlying emission mechanism.Comment: 25 pages, 18 figures, 4 table