Energy Extraction from a Black Hole and Its Influence on X-Ray Spectra

Taking into account the energy and angular momentum transferred from a rotating black hole (BH) to the inner accretion disk by the magnetic connection (MC) process, we simulate the x-ray spectra from the disk-corona system with two different magnetic configurations using the Monte Carlo method. The results show that the MC process reduces the ratio of the power dissipated in the corona to the total and softens the spectrum. The influence of the MC process is stronger with a higher BH spin, a larger accretion rate, and a larger and more centralized magnetic flux threading the disk. The comparison of the model spectra with the observational data suggests that large-scale magnetic fields accumulating in the inner disk could be a candidate explanation for the hard-to-soft state evolutions in BH binaries.