  We have carried out observations of the X-ray transient GX339-4 during its
high-soft and low-hard X-ray spectral states. Our high-resolution spectroscopic
observation in 1999 April suggests that the H-alpha line has a single-peaked
profile in the low-hard state as speculated in our previous paper. The HeII
4686 line, however, has a double-peaked profile in both the high-soft and
low-hard states. This suggests that the line-emission mechanism is different in
the two states. Our interpretation is that double-peaked lines are emitted from
a temperature-inversion layer on the accretion-disk surface when it is
irradiatively heated by soft X-rays. Single-peaked lines may be emitted from
outflow/wind matter driven by hard X-ray heating. We have constructed a simple
plane-parallel model and we use it to illustrate that a temperature-inversion
layer can be formed at the disk surface under X-ray illumination. We also
discuss the conditions required for the formation of temperature inversion and
line emission. Based on the velocity separations measured for the double-peaked
lines in the high-soft state, we propose that GX339-4 is a low-inclination
binary system. The orbital inclination is about 15 deg if the orbital period is
14.8 hours.
