We propose a sequence ( the Blazar main sequence , BMS ) that links the two main components of the Blazar class , namely , the Flat Spectrum Radio Quasars and the BL Lacertae objects , and yields all their distinctive features in a correlated way .
In this view , both type of sources are centered on a supermassive Kerr hole close to maximal spin and observed pole on .
But the FSRQs are energized by accretion at rates \dot { m } \sim 1 - 10 , and are dominated by the disk components ( thermal and electrodynamic jet-like component ) which provide outputs in excess of L \sim 10 ^ { 46 } erg s ^ { -1 } .
On the other hand , accretion levels \dot { m } \ll 1 are enough to energize the BL Lacs ; here the radiation is highly non-thermal and the power is partly contributed by the rotational energy of the central Kerr hole , with the latter and the disk together sustaining typical L \sim 10 ^ { 44 } erg s ^ { -1 } for several Gyrs .
If so , we expect the BL Lacs to show quite different evolutionary signatures from the FSRQs , and in particular , number counts close to the Euclidean shape , or flatter if the sources make a transition to the BL Lac from a FSRQ mode .
In addition , for lower \dot { m } along the BMS we expect the large scale electric fields to be less screened out , and to accelerate to higher energies fewer particles radiating at higher frequencies ; so in moving from FSRQs to BL Lacs these non-thermal radiations will peak at frequencies inversely correlated with the disk output .
For the BL Lacs such dependence implies increased scatter when one tries a correlation with the total ouput .
At its endpoint , the BMS suggests widespread objects that are radiatively silent , but still efficient in accelerating cosmic rays to ultra high energies .