Abstract:
Blazars are characterized by large intensity and spectral v
ariations across the electromagnetic
spectrum It is believed that jets emerging from them are almo
st aligned with the line-of-sight. The major-
ity of identified extragalactic sources in
γ
-ray catalogs of EGRET and Fermi are blazars. Observational
ly,
blazars can be divided into two classes: flat spectrum radio q
uasars (FSRQs) and BL Lacs. BL Lacs usually
exhibit lower
γ
-ray luminosity and harder power law spectra at
γ
-ray energies than FSRQs. We attempt to
explain the high energy properties of FSRQs and BL Lacs from F
ermi
γ
-ray space telescope observations. It
was argued previously that the difference in accretion rate
s is mainly responsible for the large mismatch in
observed luminosity in
γ
-ray. However, when intrinsic luminosities are derived by c
orrecting for beaming
effects, this difference in
γ
-ray luminosity between the two classes is significantly red
uced. In order to ex-
plain this difference in intrinsic luminosities, we propos
e that spin plays an important role in the luminosity
distribution dichotomy of BL Lacs and FSRQs. As the outflow po
wer of a blazar increases with increasing
spin of a central black hole, we suggest that the spin plays a c
rucial role in making BL Lac sources low
luminous and slow rotators compared to FSRQ sources.
