Further Studies of 1E 1740.7–2942 with ASCA
Further Studies of 1E 1740.7–2942 with ASCA
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与 ASCA 进一步研究 1E 1740.7–2942
DOI：
10.1086/307441
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
Penn. State Univ.
中科院分区：
文献类型：
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作者：
M. Sakano;K. Imanishi;M. Tsujimoto;K. Koyama;Y. M. D. Physics;Kyoto Univ. Crest Dept. Astronomy;Astrophysics;Penn. State Univ.
本文报道了大湮灭子1E1740.7 -2942在3.5年时间内用5次定点观测获得的ASCA结果。每个周期的X射线光谱都很好地符合高气柱吸收的单一幂律。X射线通量从一个周期到另一个周期变化2倍，但其他光谱参数没有显着变化。光子指数是平坦的，r = 0.9-1.3。氢NH的柱密度约为1.0 × 1023 H cm-2，铁NFe的柱密度约为1019 Fe cm-2。这些巨大的柱密度表明1 E 1740.7-2942位于银河系中心附近。柱密度比导致铁丰度比太阳比单位中的其他元素大2倍。中性铁的Kα线的等效宽度在90%置信度下小于15 eV。这表明从1 E 1740.7-2942几个秒差距内的铁柱密度小于5 × 1017 Fe cm-2。此外，推导出的氢柱密度约为视线中巨分子云的六分之一。所有这些事实都支持1 E 1740.7-2942不在分子云中，而可能在分子云的前面; X射线不是由分子云的吸积提供动力，而是像普通X射线双星一样来自伴星星星。
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 yr. 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 Γ = 0.9-1.3. The column density of hydrogen NH is ~ 1.0 × 1023 H cm-2 and that of iron NFe is ~ 1019 Fe cm-2. These large column densities indicate that 1E 1740.7-2942 is near 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 Kα 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 × 1017 Fe cm-2. In addition, the derived hydrogen column density is about one-sixth of that of giant molecular clouds in the line of sight. All these facts support the fact 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.