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| Paper: |
The Blazar’s Divide and the Properties of Fermi Blazars |
| Volume: |
427, Accretion and Ejection in AGN: a Global View |
| Page: |
249 |
| Authors: |
Ghisellini, G. |
| Abstract: |
The LAT instrument, onboard the Fermi satellite,
in its first three months of operation
detected more than 100 blazars at more than the 10σ level.
This is already a great improvement with respect to its
predecessor, the instrument EGRET onboard the Compton Gamma Ray Observatory.
Observationally, the new detections follow and confirm the so–called blazar sequence,
relating the bolometric observed non–thermal luminosity to the overall shape of
the spectral energy distribution.
We have studied the general physical properties of all these bright Fermi
blazars, and found that their jets are matter dominated, carrying a large total
power that correlates with the luminosity of their accretion disks.
We suggest that the division of blazars into the two subclasses of broad line emitting
objects (Flat Spectrum Radio Quasars) and line–less BL Lacs is a consequence of
a rather drastic change of the accretion mode, becoming radiatively inefficient
below a critical value of the accretion rate, corresponding to a disk
luminosity of ∼1 per cent of the Eddington one.
The reduction of the ionizing photons below this limit implies that the
broad line clouds, even if present, cannot produce significant broad lines,
and the object becomes a BL Lac. |
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