Magnetically Arrested Disks in Quiescent Black Hole Binaries: Formation Scenario, Observable Signatures, and Potential PeVatrons

We propose magnetically arrested disks (MADs) in quiescent black-hole (BH) binaries as the origin of multiwavelength emission, and argue that this class sources can dominate cosmic-ray spectrum around knee. X-ray luminosities Galactic BH state are far below Eddington luminosity, thus, radiatively inefficient accretion flows (RIAFs) formed inner region. Strong thermal turbulent pressures RIAFs produce outflows, which create large-scale poloidal magnetic fields. These fields carried to vicinity by rapid inflow motion, forming a MAD. Inside MAD, non-thermal protons electrons naturally accelerated reconnections or stochastic acceleration turbulence. Both emit broadband photons via synchrotron broadly consistent with optical data binaries. Moreover, up PeV energies diffusively escape from these MADs, account for intensity knee energy.