Simultaneous X-ray and optical observations of black hole X-ray binaries have shown that the light curves contain multiple correlated and anti-correlated variation components when the objects are in the hard state. In the case of the black hole X-ray binary GX 339−4, the cross correlation function (CCF) of the light curves suggests a positive correlation with an optical lag of 0.15 s and anti-correlations with an optical lag of 1 s and X-ray lag of 4 s. This indicates that the two light curves have some common signal components with different delays. In this study we extracted and reconstructed those signal components from the data for GX 339−4. The results confirmed that correlation and anti-correlation with the optical lag are two common components. However, we found that the reconstructed light curve for the anti-correlated component indicates a positively correlated variation with an X-ray lag of ∼+1 s. In addition, the CCF for this signal component shows anti-correlations not only with the optical lag, but also with the X-ray lag, which is consistent with the CCF for the data. Therefore, our results suggest that the combination of the two positively correlated components, that is, the X-ray preceding signal with the 0.15 s optical lag and the optical preceding signal with the 1 s X-ray lag, can make the observed CCF without anti-correlated signals. The optical preceding signal may be caused by synchrotron emission in a magnetically dominated accretion flow or in a jet, while further study is required to understand the mechanism of the X-ray time lag.

中文翻译：

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从 GX 339−4 的 X 射线和光学光变曲线中提取常见信号分量：反相关的新观点

同时对黑洞X射线双星的X射线和光学观测表明，当物体处于坚硬状态时，光变曲线包含多个相关和反相关的变化分量。在黑洞 X 射线双星 GX 339-4 的情况下，光变曲线的互相关函数 (CCF) 表明与 0.15 s 的光学滞后呈正相关，与 1 s 的光学滞后呈反相关， X 射线延迟 4 秒。这表明两条光变曲线具有一些具有不同延迟的共同信号分量。在这项研究中，我们从 GX 339-4 的数据中提取并重建了这些信号分量。结果证实，与光学滞后的相关性和反相关性是两个常见的成分。然而，我们发现反相关分量的重建光曲线表明正相关的变化与~+1 s 的 X 射线滞后。此外，该信号分量的 CCF 不仅与光学滞后，而且与 X 射线滞后呈反相关，这与数据的 CCF 一致。因此，我们的结果表明，两个正相关分量的组合，即具有 0.15 s 光学滞后的 X 射线超前信号和具有 1 s X 射线滞后的光学超前信号，可以使观察到的 CCF 没有反相关信号。光学先行信号可能是由磁主导的吸积流或射流中的同步加速器发射引起的，而需要进一步研究以了解 X 射线时滞的机制。