  (abridged) Afterglow light curves are constructed analytically for realistic
gamma-ray burst remnants decelerating in either a homogeneous interstellar
medium or a stellar wind environment, taking into account the radiative loss of
the blast wave, which affects the temporal behaviors significantly. Inverse
Compton scattering is considered. The inverse Compton effect prolongs the
fast-cooling phase markedly, during which the relativistic shock is
semi-radiative and the radiation efficiency is approximately constant. It is
further shown that the shock is still semi-radiative for quite a long time
after it transits into the slow-cooling phase. The temporal decaying index of
the X-ray afterglow light curve in this semi-radiative phase is more consistent
with the observed $<\alpha_{X}> \sim 1.3$ than the commonly used adiabatic one.
To manifest as a bump or even dominant in the X-ray afterglows during the
relativistic stage, it is required that the density should be larger than about
1-10 cm$^{-3}$ in the interstellar medium case, or the wind parameter
$A_{\ast}$ should be larger than unity in the stellar wind case.
