  Iron spectral features are thought to be the best tracer of a progenitor of
gamma-ray bursts (GRBs). The detections of spectral features such as an iron
line and/or a Radiative Recombination edge and Continuum (RRC) were reported in
four X-ray afterglows of GRBs. However their properties were different each
other burst by burst. For example, Chandra observation of GRB 991216 reported
both the strong H-like iron line together with its RRC. On the contrary,
Yoshida et al. (2001) report only a detection of the strong RRC in GRB 970828
with ASCA. Since it is difficult to produce the strong RRC, we have to consider
special condition for the line and/or the RRC forming region. In this paper, we
point out a possibility of a ``non-equilibrium ionization state'' for the line
and the RRC forming region.
