A team led by Prof. MAO Jirong from the Yunnan Observatories of the Chinese Academy of Sciences, in collaboration with international researchers, has recently published a study in The Astrophysical Journal confirming the presence of a standing shock in low-angular-momentum black hole accretion modes. Using general relativistic magnetohydrodynamic (GRMHD) simulations, the researchers identified the stationary shock phenomenon in accretion flows around black holes.

While it has long been hypothesized that shocks could form in accretion flows near central black holes—with "standing shocks" being defined by their fixed positions—scientific consensus on their existence has remained elusive. 

To address this gap, the team conducted both two- and three-dimensional MHD simulations within the framework of general relativity, focusing on black hole accretion dynamics. They found that in low-angular-momentum accretion modes, a shock forms consistently near the central black hole and maintains a stable position throughout the accretion process—providing direct evidence for the existence of standing shocks.

Furthermore, standing shocks appear in "standard and normal evolution" (SANE) accretion disks but are absent in "magnetic arrested disk" (MAD) systems, a distinction that refines models of black hole accretion.

The study also links standing shocks to a well-documented astrophysical phenomenon: quasi-periodic oscillations (QPOs). As standing shocks oscillate at fixed locations, they accelerate charged particles; the radiation emitted by these accelerated particles matches the periodic signals observed in X-ray binaries and active galactic nuclei—offering a new explanation for QPO origins.

"This study advances our understanding of accretion physics, a field central to unraveling black hole behavior and galaxy evolution," said Prof. MAO.

This work was supported by the National Key R&D Program of China, the Natural Science Foundation of China, and the Yunnan Revitalization Talent Support Program.