  Aims: We investigate the behavior of the frequency-centered light curves
expected within the standard model of Gamma Ray Bursts allowing the maximum
electron energy to be a free parameter permitted to take low values. Methods:
We solve the spatially averaged kinetic equations which describe the
simultaneous evolution of particles and photons, obtaining the multi-wavelength
spectra as a function of time. From these we construct the frequency-centered
light curves giving emphasis in the X-ray and optical bands. Results: We show
that in cases where the maximum electron energy takes low values, the produced
X-ray light curves show a plateau as the synchrotron component gives its place
to the Synhro Self-Compton one in the X-ray band.
