![]() Through numerical simulations of the outburst of the black hole X-ray binary, it was discovered that as the outburst approaches the end, the irradiation of hard X-rays causes more accreting material from the far outer region to fall toward the black hole due to instability. You Bei, first author and co-corresponding author of the study.Īdditionally, the research team observed an unprecedented delay (about 17 days) between the optical emission from the outer region of the accretion flow and the hard X-rays from the hot accretion flow. This represents the direct observational evidence for the existence of a magnetically arrested disk,” said Assoc. “Our study for the first time reveals the process of magnetic field transport in the accretion flow and the process of MAD formation in the vicinity of the black hole. This leads to a rapid strengthening of the magnetic field near the black hole, resulting in the formation of a MAD approximately eight days after the peak of the hard X-ray emission. The greater the radial extent of the hot accretion flow, the greater the increase in the magnetic field. ![]() These observations indicate that the weak magnetic field in the outer region of the accretion disk is carried into the inner region by the hot gas, and the radial extent of the hot accretion flow rapidly expands as the accretion rate decreases. Such a long delay between radio emission from the jet and the hard X-rays from the hot accretion flow is unprecedented. They observed that the hard X-ray emission exhibited a peak that was followed by a peak in radio emission eight days later. In this study, the researchers performed a multi-wavelength data analysis of the outburst of the black hole X-ray binary MAXI J1820+070. As a result, these types of binary star systems are often referred to as black hole X-ray binaries. However, they occasionally enter an outburst period that can last for several months or even years, producing bright X-rays. Most of the time, these black holes are in a quiescent state, emitting extremely weak electromagnetic radiation. These black holes generally have a mass about ten times that of the Sun. Astronomers have detected stellar-mass black holes in many binary star systems in the Milky Way. In addition to the supermassive black holes at the centers of nearly every galaxy, there are also many more stellar-mass black holes in the universe. Schematic representation of accretion flow, magnetic field, and jet evolution. However, no direct observational evidence for the existence of a MAD was available, and MAD formation and magnetic transport mechanisms remained mysteries. The MAD theory was proposed many years ago and has successfully explained some observational phenomena related to black hole accretion. This phenomenon is known as a magnetically arrested disk. Therefore, in the inner region of the accretion flow near the black hole, when the magnetic field reaches a certain strength, the accreted matter becomes trapped by the magnetic field and cannot freely fall into the black hole. The outward magnetic force on the accretion flow increases and counteracts the inward gravitational pull from the black hole. Previous theories suggested that as the accreting gas continuously brings in weak external magnetic fields, the magnetic field progressively strengthens towards the inner region of the accretion flow. As the black hole accretes gas, it also drags the magnetic field inwards. However, there are “unseen” magnetic fields around the black hole. This radiation can be observed by ground-based and space telescopes, allowing us to “see” the black hole. The viscous processes within the accretion flow effectively release gravitational potential energy, with a portion of the energy being converted into multi-wavelength radiation. The process of a black hole capturing gas is known as “accretion”, and the gas falling into the black hole is referred to as an accretion flow. Multi-wavelength light curves (showing the change in brightness over time) of the black hole X-ray binary MAXI J1820+070.
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