  Time-dependent thermal effects should accompany standard non-thermal
afterglows of GRB when gamma-rays pass through inhomogeneous surroundings of
the GRB site. Thermal relaxation of an optically thin plasma is calculated
using time-dependent collisional ionization of the plasma ion species. X-ray
emission lines are similar to those found in the fading X-ray afterglow of GRB
011211. Thermal relaxation of clouds or shells around the GRB site could also
contribute to the varying late optical GRB afterglows, such as in GRB021004 and
GRB030329.
