Spectrum of two component flows around a super-massive black hole: an   application to M87
  We calculate the spectra of two-component accretion flows around black holes of various masses, from quasars to nano-quasars. Specifically, we fit the observational data of M87 very satisfactorily using our model and find that the spectrum may be well fitted by a sub-Keplerian component alone, and there is little need of any Keplerian component. The non-thermal distribution of electrons produced by their acceleration across the standing shock in the sub-Keplerian component is enough to produce the observed flat spectrum through the synchrotron radiation. 
Samir Mandal and Sandip K. Chakrabarti