We report results of an analysis of the black hole (BH) candidate source X1755−338 made in 1989, 1990, and 1991 with Ginga, and in 1995 with ASCA. The spectra were well represented by a model consisting of a soft thermal emission from an accretion disk and a hard X-ray tail. The normalization of the multi-color disk, related to the inner disk radius, was similar to each other. The unabsorbed X-ray fluxes from the disk component in the 0.01–10 keV band were estimated to be 1.3 × 10−9, 3.0 × 10−9, 9.8 × 10−10, and 2.4 × 10−9 erg s−1 cm−2 in 1989, 1990, 1991, and 1995, respectively, and are proportional to $kT_{\rm in}^4$, where kTin is a temperature at the inner disk radius. Based on the standard accretion disk model for a non-rotating BH, our results suggest either a small BH mass or a large inclination angle. Otherwise, X1755−338 is a rotating BH. The hard X-ray intensity was found to be variable, while the soft X-ray intensity was stable. Although previous work showed the existence of an iron line at 6.7 keV, no clear iron line feature was found in any of the spectra. We infer that most of the iron line flux reported in the previous work was due to contamination of the Galactic diffuse X-ray emission.

中文翻译：

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1989-1995 年观测到的候选黑洞 X1755-338 的光谱和时间特性

我们报告了 1989、1990 和 1991 年用 Ginga 和 1995 年用 ASCA 对黑洞 (BH) 候选源 X1755−338 进行的分析结果。由吸积盘的软热发射和硬 X 射线尾组成的模型很好地表示了光谱。与内盘半径相关的多色盘的归一化彼此相似。在 0.01-10 keV 波段中，来自圆盘组件的未吸收 X 射线通量估计为 1.3 × 10-9、3.0 × 10-9、9.8 × 10-10 和 2.4 × 10-9 erg s-1 cm -2 分别在 1989、1990、1991 和 1995 年，并且与 $kT_{\rm in}^4$ 成正比，其中 kTin 是内盘半径处的温度。基于非旋转 BH 的标准吸积盘模型，我们的结果表明 BH 质量小或倾角大。否则，X1755−338 是一个旋转 BH。发现硬X射线强度是可变的，而软X射线强度是稳定的。尽管之前的工作表明存在 6.7 keV 的铁线，但在任何光谱中都没有发现明显的铁线特征。我们推断，之前工作中报告的大部分铁线通量是由于银河系漫射 X 射线发射的污染。