Correlation between 3:2 QPO Pairs and Jets in Black Hole X-Ray Binaries

We argue, following our earlier works (the "CEBZMC model"), that the phenomenon of twin-peak high-frequency quasi-periodic oscillations (QPOs) observed in black hole X-ray binaries is caused by magnetic coupling (MC) between the accretion disk and the black hole (BH). Due to MC, two bright spots occur at separate radial locations rin and rout at the disk surface, energized by a kind of Blandford-Znajek mechanism (BZ). We assume, following the Kluzniak-Abramowicz QPO resonance model, that the Keplerian frequencies at these two locations are in the 3 : 2 ratio. With this assumption, we estimate the BH spins in several sources, including GRO J1655-40, GRS 1915+105, XTE J1550-564, H1743-322, and Sgr A*. We give an interpretation of the "jet line" in the hardness-intensity plane, discussing the parameter space consisting of the BH spin and the power-law index for the variation of the large-scale magnetic field in the disk. Furthermore, we propose a new scenario for the spectral state transitions in BH X-ray binaries based on fluctuations in the densities of the accreting plasma from a companion star.