The accreting black-hole binary XTE J1752-223 was observed in a stable hard state for 25 d by RXTE, yielding a 3-140 keV spectrum of unprecedented statistical quality and accuracy. A fit to this spectrum was reported, requiring a single Comptonization spectrum reflecting from a disk extending close to the innermost stable circular orbit. We have revisited those fits, and found that the $\leq$10 keV band is much better fitted by a reflection from a disk with the inner radius $\gtrsim$100 gravitational radii. Our model underpredicts the spectrum at $>$10 keV by $<$15%. We argue that the most plausible explanation of it is that the source is inhomogeneous, with the local spectra hardening with the decreasing radius, as found in other accreting black-hole binaries. Thus, our results indicate that models with single-region Comptonization cannot fully describe broad-band X-ray spectra. We have also studied the contemporaneous 0.55-6 keV spectrum from the Swift/XRT and found it is well fitted by an absorbed featureless power law down to 1 keV and a disk blackbody spectrum with the innermost temperature of 0.1 keV at lower energies. The normalization of the disk blackbody corresponds to the inner radius of $\sim$100 gravitational radii as well as its temperature corresponds to irradiation of the truncated disk by a hot inner flow below that radius.

中文翻译：

---

XTE J1752-223硬态的磁盘是否延伸到最里面的稳定圆轨道？

RXTE 在 25 天的稳定硬态下观察到吸积的黑洞双星 XTE J1752-223，产生了 3-140 keV 的光谱，具有前所未有的统计质量和准确性。据报道，该光谱适合该光谱，需要从靠近最内部稳定圆形轨道延伸的圆盘反射的单个 Comptonization 光谱。我们重新审视了这些拟合，发现 $\leq$10 keV 带更适合由内半径为 $\gtrsim$100 引力半径的圆盘的反射拟合。我们的模型低估了 $>$10 keV 的频谱 $<$15%。我们认为最合理的解释是源是不均匀的，局部光谱随着半径的减小而硬化，就像在其他吸积黑洞双星中发现的那样。因此，我们的结果表明，具有单区域 Comptonization 的模型不能完全描述宽带 X 射线光谱。我们还研究了来自 Swift/XRT 的同期 0.55-6 keV 光谱，发现它非常适合低至 1 keV 的吸收无特征幂律和在较低能量下最内层温度为 0.1 keV 的盘状黑体光谱。圆盘黑体的归一化对应于 $\sim$100 引力半径的内半径，其温度对应于该半径以下的热内流对截断圆盘的辐射。在较低能量下为 1 keV。圆盘黑体的归一化对应于 $\sim$100 引力半径的内半径，其温度对应于该半径以下的热内流对截断圆盘的辐射。在较低能量下为 1 keV。圆盘黑体的归一化对应于 $\sim$100 引力半径的内半径，其温度对应于该半径以下的热内流对截断圆盘的辐射。