Magnetic flares and the optical variability of the X-ray transient XTE J1118+480
Magnetic flares and the optical variability of the X-ray transient XTE J1118+480
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X 射线瞬态 XTE J1118 480 的磁耀斑和光学变化
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
A. Fabian
中科院分区：
文献类型：
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作者：
A. Merloni;T. Matteo;A. Fabian
在 X 射线瞬态 XTE J1118+480 的光学和 X 射线光曲线中同时存在周期为 ∼10 s 的强准周期振荡，这表明光通量的很大一部分源自吸积流的内部，大部分 X 射线都是在此处产生的。我们提出了吸积盘日冕中的磁耀斑模型，其中热旋回同步加速器发射对光发射有显着贡献，而 X 射线是由底层盘中耗散和同步加速器过程本身产生的软光子的逆康普顿散射产生的。考虑到观测限制，我们估计了日冕温度、光学深度和磁场强度的值，以及源的吸积率。在我们的模型中，我们预测光学和硬 X 射线变异性之间的相关性以及光学和软 X 射线之间的反相关性。我们还预计耀斑时间尺度（约数十毫秒）上的光学变化，其功率密度谱与 X 射线波段中观察到的相似。最后，我们使用可用的光学/极紫外/X射线光谱能量分布和低频时间变化来讨论光学厚盘内半径的限制。
The simultaneous presence of a strong quasi-periodic oscillation, of period ∼10 s, in the optical and X-ray light curves of the X-ray transient XTE J1118+480 suggests that a significant fraction of the optical flux originates from the inner part of the accretion flow, where most of the X-rays are produced. We present a model of magnetic flares in an accretion disc corona where thermal cyclo-synchrotron emission contributes significantly to the optical emission, while the X-rays are produced by inverse Compton scattering of the soft photons produced by dissipation in the underlying disc and by the synchrotron process itself. Given the observational constraints, we estimate the values for the coronal temperature, optical depth and magnetic field intensity, as well as the accretion rate for the source. Within our model we predict a correlation between optical and hard X-ray variability and an anticorrelation between optical and soft X-rays. We also expect optical variability on flaring time-scales (∼tens of ms), with a power-density spectrum similar to that observed in the X-ray band. Finally, we use both the available optical/extreme-ultraviolet/X-ray spectral energy distribution and the low-frequency time variability to discuss limits on the inner radius of the optically thick disc.