  Bimodal spectral energy distributions (SEDs) of gamma-ray burst (GRB)
afterglow of GRBs 190114C, 130427A and 180720B confirm that they are originated
from the synchrotron emission (Syn) and synchrotron self-Compton Scattering
process (SSC) of electrons accelerated in the jets. The radiation mechanism and
the physics of the observed spectrum-luminosity/energy relations of GRBs remain
as open questions. By extracting the Syn component through fitting their early
afterglow SEDs with the Syn+SSC model, we find that their luminosity ($L_{\rm
syn}$), peak energy ($E_{\rm p,syn,z}$), and the Lorentz factor of the
afterglow fireball ($\Gamma_t$) follow the $L_{\rm p, iso}-E_{\rm
p,z}-\Gamma_{0}$ relation of prompt gamma-rays, where $L_{\rm p, iso}$ is the
isotropic luminosity, $E_{\rm p, z}$ is the peak energy of the $\nu f_\nu$
spectrum in the burst frame, and $\Gamma_0$ is the initial Lorentz factor of
the fireball. To examine whether late afterglows is consistent with this
relation, we calculate the synchrotron component at late afterglows. It is
found that they also follow the same $L_{\rm p, iso}-E_{\rm p,z}-\Gamma_{0}$
relation, albeit they are not consistent with the $L_{\rm p, iso}-E_{\rm p,z}$
relation. Our results may imply that the $L_{\rm p, iso}-E_{\rm
p,z}-\Gamma_{0}$ would be an universal feature of synchrotron radiations of
electrons accelerated in GRB jets throughout the prompt and afterglow phases
among GRBs. Its origin is not fully understood and possible explanations are
briefly discussed.

High Energy Astrophysical Phenomena