4 2009 Fermi Symposium, Washington, D.C., Nov. 2-5
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Figure 1: (Left) The preliminary signiﬁcance measured from each of the 49 non-detected candidates using standard
analysis cuts. The curve shows a Gaussian distribution, wit h mean zero and standard deviation one, normalized to the
number of blazars. A similar result is obtained using analys is cuts optimized for soft-spectrum sources. (Right) The
distribution of ﬂux upper limits for the non-detected blaza rs in percentage of Crab Nebula ﬂux above the observation
threshold. The time-weighted average limit is less than ∼ 2% Crab ﬂux.
since the launch of Fermi include LAT detections. In
addition, several MWL campaigns on the well-studied
VHE blazars Mkn 421 and Mkn 501 (please see the
contributions of D. Gall and A. Konopelko in these
proceedings) were also performed. Highlights of these
campaigns include:
• 1ES 2344+514: A major (50% Crab) VHE ﬂare,
along with correlations of the VHE and X-ray
ﬂux were observed from this HBL. The VHE
and X-ray spectra harden during bright states,
and a synchrotron self-Compton (SSC) model
can explain the observed SED in both the high
and low states [26].
• 1ES 1218+304: This HBL ﬂared during VER-
ITAS MWL observations. Its unusually hard
VHE spectrum strongly constrains the EBL.
The observed ﬂaring rules out kpc-scale jet emis-
sion as the explanation of the spectral hardness
and places the EBL constraints on more solid-
footing [27, 28].
• 1ES 0806+524: The observed SED of this new
VHE HBL can be explained by an SSC model
[16].
• W Comae: This IBL, the ﬁrst discovered at
VHE, ﬂared twice in 2008 [14, 15]. Modeling of
the SED is improved by including an external-
Compton (EC) component in an SSC interpre-
tation.
• 3C 66A: This IBL ﬂared at VHE and MeV-GeV
energies in 2008[17, 18]. Similar to W Comae
and PKS 1424+240, modeling of observed SED
suggests a strong EC component in addition to
an SSC component.
• Mkn 421: This HBL exhibited major ﬂaring be-
havior for several months in 2008. Correlations
of the VHE and X-ray ﬂux were observed, along
with spectral hardening with increased ﬂux in
both bands [29].
• RGB J0710+591: Modeling the SED of this
HBL with an SSC model yields a good ﬁt to
the data. The inclusion of an external Compton
component does not improve the ﬁt.
• PKS 1424+240: The broadband SED of this IBL
(at unknown redshift) is well described by an
SSC model favoring a redshift of less than 0.1
[21]. Using the photon index measured with
Fermi-LAT in combination with recent EBL ab-
sorption models, the VERITAS data indicate
that the redshift of PKS 1424+240 is less than
0.66.
8. Conclusions
The ﬁrst two years of the VERITAS blazar KSP
were highly successful. Highlights include the detec-
tion of more than a 16 VHE blazars with the obser-
vations almost always having contemporaneous MWL
data. Among these detections are 8 VHE blazar dis-
coveries, including the ﬁrst three IBLs known to emit
VHEγ-rays. All but a handful of the blazars on the
initial VERITAS discovery target list were observed,
and the ﬂux limits generated for those not VHE de-
tected are generally the most-constraining ever. The
excess seen in the stacked blazar analysis suggests
that the initial direction of the VERITAS discovery
program was well justiﬁed, and that follow-up obser-
vations of many of these initial targets will result in
VHE discoveries. In addition, the Fermi-LAT is iden-
tifying many new compelling targets for the VERITAS
blazar discovery program. These new candidates have
already resulted in 3 VHE blazar discoveries. The
future of the VERITAS blazar discovery program is
clearly very bright.
The MWL aspect of the VERITAS blazar KSP has
also been highly successful. Every VERITAS obser-
vation of a known, or newly discovered, VHE blazar
has been accompanied by contemporaneous MWL ob-
servations. These data have resulted in the identiﬁca-