We report the ASCA results of the Great Annihilator 1E 1740.7 - 2942 obtained with five pointing observations in a time span of 3.5 years .
The X-ray spectrum for each period is well fitted with a single power-law absorbed by a high column of gas .
The X-ray flux changes by a factor of 2 from period to period , but the other spectral parameters show no significant change .
The photon index is flat with \Gamma = 0.9–1.3 .
The column densities of hydrogen N _ { H } is \sim 1.0 \times 10 ^ { 23 } { H } { cm } ^ { -2 } and that of iron N _ { Fe } is \sim 10 ^ { 19 } { Fe } { cm } ^ { -2 } .
These large column densities indicate that 1E 1740.7 - 2942 is near at the Galactic Center .
The column density ratio leads the iron abundance to be 2 times larger than the other elements in a unit of the solar ratio .
The equivalent width of the K \alpha -line from a neutral iron is less than 15 eV in 90 % confidence .
This indicates that the iron column density within several parsecs from 1E 1740.7 - 2942 is less than 5 \times 10 ^ { 17 } { Fe } { cm } ^ { -2 } .
In addition , the derived hydrogen column density is about 1/6 of that of giant molecular clouds in the line of sight .
All these facts support that 1E 1740.7 - 2942 is not in a molecular cloud , but possibly in front of it ; the X-rays are not powered by accretion from a molecular cloud , but from a companion star like ordinary X-ray binaries .