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arXiv · 2111.13642

Synchronous X-ray/Optical QPOs from the Black Hole LMXB MAXI J1820+070

Jessymol K. Thomas·David A. H. Buckley·Philip A. Charles·John A. Paice·Stephen B. Potter·James F. Steiner·Jean-Pierre Lasota·P. Gandhi·Lian Tao·Xiang Ma·Yi-Jung Yang·Youli Tuo·Shuang-Nan Zhang
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Abstract

We present high-speed optical photometry from SAAO and SALT on the black hole LMXB \MAXI (ASSASN-18ey), some of it simultaneous with NICER, Swift and Insight-HXMT X-ray coverage. We detect optical Quasi-Periodic Oscillations (QPOs) that move to higher frequencies as the outburst progresses, tracking both the frequency and evolution of similar X-ray QPOs previously reported. Correlated X-ray/optical data reveal a complex pattern of lags, including an anti-correlation and a sub-second lag that evolve over the first few weeks of outburst. They also show correlated components separated by a lag equal to the QPO period roughly centered on zero lag, implying that the inter-band variability is strongly and consistently affected by these QPOs at a constant phase lag of roughly +/- pi. The synchronisation of X-ray and optical QPOs indicates that they must be produced in regions physically very close to each other; we thus propose that they can be explained by a precessing jet model, based on analogies with V404 Cyg and MAXI J1348-630.

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Jessymol K. Thomas, David A. H. Buckley, Philip A. Charles, John A. Paice, Stephen B. Potter, James F. Steiner, Jean-Pierre Lasota, P. Gandhi, Lian Tao, Xiang Ma, Yi-Jung Yang, Youli Tuo, Shuang-Nan Zhang. 2021-11-26. Synchronous X-ray/Optical QPOs from the Black Hole LMXB MAXI J1820+070. https://doi.org/10.1093/mnrasl%2Fslab132

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