Figure 7

Figure 7: The innermost part of the disk. In the Shakura–Sunyaev and Novikov–Thorne models, the locations of the maximum pressure (a.k.a. the center) rcenter and the cusp rcusp, as well as the sonic radius rsound, are assumed to coincide with the ISCO. Furthermore, the angular momentum is assumed to be strictly Keplerian outside the ISCO and constant inside it. In real flows, r ⁄= r ⁄= r ⁄= ISCO center cusp sound, and angular momentum is super-Keplerian between r cusp and rcenter. Image reproduced by permission from [9], copyright by ESO.