Chinese Acad Sci, Inst High Energy Phys, Key Lab Particle Astrophys, Beijing 100049, Peoples R China
; Chinese Acad Sci, Grad Sch, Beijing 100049, Peoples R China
; Chinese Acad Sci, Natl Astron Observ, Beijing 100012, Peoples R China
We compiled a sample of 98 radio-quiet active galactic nuclei observed by ASCA, Chandra, XMM-Newton, INTEGRAL and Swift with the aim of testing the formation of hot corona and the magnetic shear stress operating in a disk-corona system. We found a strong correlation between the hard X-ray luminosity, bolometric luminosity L-Bol and Eddington luminosity LEdd, in the sense that the fraction f of hard X-ray to the bolometfic luminosity is inversely proportional to the Eddington ratio. This correlation favors the shear stress tensor being of the form of tr phi proportional to P-gas, with which the disk-corona structure is stable.