Mass estimate of the Swift J 164449.3+573451 supermassive black hole   based on the 3:2 QPO resonance hypothesis
  A dormant Swift source J 164449.3+573451 (Sw 164449+57)recently experienced a powerful outburst, caused most probably by a tidal disruption of a star by the super-massive black hole at the center of the source. During the outburst, a quasi periodic oscillation (QPO) was detected in the observed X-ray flux from Sw 164449+57. We show that if the observed QPO belongs to a "3:2 twin peak QPO" (with the second frequency not observed), the mass of the black hole in Sw 164449+57 is rather low, M ~ 10^5 M_sun, and the source belongs to a class of intermediate mass black holes. The low mass of the source has been pointed out previously by several authors. 
M. A. Abramowicz and F. K. Liu
astro-ph.HE gr-qc