  The absorption feature detected in the prompt X-ray emission of GRB990705 has
important consequences for its circum-burst environment and therefore on its
afterglows. Here we investigate whether the circum-burst environment
constrained by the absorption feature could be consistent with the observed
H-band afterglow, which exhibits an earlier power law decay but a much faster
decay about one day after the burst. Two possible geometries of the
afterglow-emitting regions are suggested: 1) afterglow emission produced by the
impact of the fireball on the surrounding torus, which serves as the absorbing
material of the X-ray feature, as would be expected in the models involving
that a supernova explosion precedes the gamma-ray burst by some time;
2)afterglow emission produced in the dense circum-burst medium inside the
torus. In case 1), the faster decay at the later time is attributed to the
disappearance of the shock due to the counter-pressure in the hot torus
illuminated by the burst and afterglow photons. For case 2), the circum-burst
medium density is found to be very high ($n\ga 10^4-10^5 {\rm cm^{-3}}$) if the
emitting plasma is a jet or even higher if it is spherical. Future better
observations of afterglows of GRBs that have absorption features might make it
possible to make a more definite choice between these two scenarios.
