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arXiv · 2309.00200

Observations of a black hole X-ray binary indicate formation of a magnetically arrested disk

Bei You·Xinwu Cao·Zhen Yan·Jean-Marie Hameury·Bozena Czerny·Yue Wu·Tianyu Xia·Marek Sikora·Shuang-Nan Zhang·Pu Du·Piotr T. Zycki
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Abstract

Accretion of material onto a black hole drags any magnetic fields present inwards, increasing their strength. Theory predicts that sufficiently strong magnetic fields can halt the accretion flow, producing a magnetically arrested disk (MAD). We analyze archival multi-wavelength observations of an outburst from the black hole X-ray binary MAXI J1820+070 in 2018. The radio and optical fluxes are delayed by about 8 and 17 days respectively, compared to the X-ray flux. We interpret this as evidence for the formation of a MAD. In this scenario, the magnetic field is amplified by an expanding corona, forming a MAD around the time of the radio peak. The optical delay is then due to thermal viscous instability in the outer disk.

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Bei You, Xinwu Cao, Zhen Yan, Jean-Marie Hameury, Bozena Czerny, Yue Wu, Tianyu Xia, Marek Sikora, Shuang-Nan Zhang, Pu Du, Piotr T. Zycki. 2023-09-01. Observations of a black hole X-ray binary indicate formation of a magnetically arrested disk. https://doi.org/10.1126/science.abo4504

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