Simultaneous optical/X-ray study of GS 1354-64 (=BW Cir) during hard outburst: evidence for optical cyclo-synchrotron emission from the hot accretion flow

Simultaneous optical/X-ray study of GS 1354-64 (=BW Cir) during hard outburst: evidence for optical cyclo-synchrotron emission from the hot accretion flow
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硬爆发期间 GS 1354-64 (=BW Cir) 的同步光学/X 射线研究：来自热吸积流的光学回旋同步加速器发射的证据

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发表时间：
2017
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通讯作者：
R. Misra
R. Misra
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作者：
M. Pahari;P. Gandhi;P. Charles;M. Kotze;D. Altamirano;R. Misra

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我们介绍了同时使用光学(SALT)和X射线(SWIFT和 GS1354-/BW CIR在2015年硬状态期间的积分)观测 突然爆发。在上升阶段，光学/X射线时间序列显示 与X射线光子的强反关联滞后于光学。光学和 X射线功率谱显示准周期振荡的频率为 ~18 MHz，置信度至少99%。同时拟和 0.5-1000keV范围内的SWIFT/XRT和积分谱显示 非热、幂定律控制的(&gt；90%)光谱，具有硬 幂指数为1.48+/-0.03，内盘温度为0.12+/- 0.01keV，内盘半径约3000公里。所有证据都一致 在非热、热电子云中的回旋同步辐射 扩展到~100 Schwarzschild半径是一个主要的物理过程 光学光子的起源。在大约一个月后的爆发高峰期， 当X射线通量上升和光学下降时，明显的特征是 在光学/X射线相关消失和光学自相关 变宽了。虽然从X射线功率谱中观察到~0.19赫兹的QPO， 光学可变性主要受宽带噪声的影响，而 内部阀瓣温度升高。这些结果支持改变 突出上升和峰值之间的主要光发射源， 与圆盘移动时热流减弱相一致。
We present results from simultaneous optical (SALT) and X-ray (Swift and INTEGRAL) observations of GS 1354-64/BW Cir during the 2015 hard state outburst. During the rising phase, optical/X-ray time series show a strong anti-correlation with X-ray photons lagging optical. Optical and X-ray power spectra show quasi-periodic oscillations at a frequency of ~18 mHz with a confidence level of at least 99%. Simultaneous fitting of Swift/XRT and INTEGRAL spectra in the range 0.5-1000 keV shows non-thermal, power-law dominated (> 90%) spectra with a hard power-law index of 1.48 +/- 0.03, inner disc temperature of 0.12 +/- 0.01 keV and inner disc radius of ~3000 km. All evidence is consistent with cyclo-synchrotron radiation in a non-thermal, hot electron cloud extending to ~100 Schwarzschild radii being a major physical process for the origin of optical photons. At outburst peak about one month later, when the X-ray flux rises and the optical drops, the apparent features in the optical/X-ray correlation vanish and the optical auto correlation widens. Although ~0.19 Hz QPO is observed from the X-ray power spectra, the optical variability is dominated by the broadband noise, and the inner disc temperature increases. These results support a change in the dominant optical emission source between outburst rise and peak, consistent with a weakening of hot flow as the disc moves in.