  The X-ray binary pulsar GX 1+4 was observed with Ginga every year from 1987
to 1991, and with ASCA in 1994. During the Ginga observations, GX 1+4 was in
the steady spindown phase, while the X-ray flux was not steady. The X-ray
luminosity decreased down to L = 2.7\times10^{36} erg s^{-1} in 1991, after the
peak activity of L = 1.2\times10^{37} erg s^{-1} in 1989. On the other hand,
the absorption column density showed a drastic increase over the Ginga
observation series. It reached a maximum of 1.4\times10^{24} cm^{-2} in 1991,
indicating a rapid accumulation of matter in the vicinity of the source. The
ASCA observation was performed on 1994/09/15, a month before the transition
into a spinup phase. The source brightened again to L = 10^{37} erg s^{-1}. The
absorption column density was observed to decrease for the first time to
2\times10^{23} cm^{-2}. The ionization degree of iron in the absorbing matter
was determined to be Fe I--Fe IV using the ratio of the line-center energy to
the absorption-edge energy. The low ionization degree is consistent with an
absorbing matter distribution extending 10^{12} cm from the source. We compared
the results with optical observations, and found the optical data also supports
the picture. Based on the geometrical model, possible causes of the bimodal
behavior of the source are discussed.

Astrophysics