Mass and Spin of GRS 1915+105 Based on a Resonance Model of QPOs
  We demonstrate that the four high-frequency QPOs observed in GRS 1915+105 can be interpreted as the oscillation modes on disks which non-linearly and resonantly interact with a warp. The warp is assumed to be a low-frequency global pattern on the disk. This identification suggests that the relevant mass, $M$, and spin, $a$, of GRS 1915+105 are, $M=13\sim 14 M_\odot$ and $a=0\sim 0.15$ 
Shoji Kato