Observational evidence for a high-energy Compton cloud in GRO J1655-40 under a high accretion rate
Observational evidence for a high-energy Compton cloud in GRO J1655-40 under a high accretion rate
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高吸积率下 GRO J1655-40 中高能康普顿云的观测证据
DOI：
10.1093/pasj/55.1.273
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
K. Makishima
中科院分区：
文献类型：
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作者：
Y. Kobayashi;A. Kubota;K. Nakazawa;Tadayuki Takahashi;K. Makishima
本文报道了GRO J1655−-40的观测结果，它是根据1996年至1997年爆发期间用主成分分析装置和HEXTE星上的RXTE获得的X射线能谱。参照40-150keV X射线光度L40-150，选取了6个典型光谱进行了分析。当L40-150充分低于∼5×1036erg S−1(假定距离为3.2kpc，发射各向同性)时，3-150keV的PCA/HEXTE谱可以用一个标准的光谱模型很好地描述，该模型由一个光学厚度的盘谱和一个幂函数尾部组成。当L40-150超过5×1036erg S−1时，标准模型不能重现联合谱，这是因为六角线的光谱有轻微的翻转。当用∼40keV的破缺能量的破缺的幂定律模型或截断能量在190-300keV的指数截断的幂定律模型代替幂定律分量时，成功的拟合被恢复。通过采用热康普顿化组件进一步改进了拟合，其中康普顿云的电子温度和光学厚度估计分别为70-85keV和0.45-0.65。这些结果为热高能电子的存在提供了强有力的证据，并再次证实了强盘压密化的图景。
Observational results on GRO J1655−40 are reported, based on the X-ray spectra obtained with the PCA and the HEXTE on-board RXTE during its 1996–1997 outburst. By referring to the 40–150 keV X-ray luminosity, L40–150, six typical spectra were selected and analyzed. When L40–150 is sufficiently below ∼ 5× 1036erg s−1 (assuming a distance of 3.2 kpc and an isotropic emission), the 3–150 keV PCA/HEXTE spectra are well described by a standard spectral model consisting of an optically-thick disk spectrum and a power-law tail. When L40–150 exceeds 5× 1036 erg s−1, the standard model fails to reproduce the joint spectrum, due to a mild turn-over in the HEXTE spectrum. Successful fits are recovered when the power-law component is replaced by a broken powerlaw model with the break energy at ∼ 40 keV, or by an exponentially cutoff power-law model with the cutoff energy at 190–300 keV. The fits are further improved by employing a thermal Comptonization component, wherein the electron temperature and optical depth of the Compton cloud are estimated to be 70–85 keV and 0.45–0.65, respectively. These results provide strong evidence for the existence of thermal high-energy electrons, and reconfirm the picture of strong disk Comptonization.