Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: VERITAS Observations of a Very High Energy Gamma-ray Flare from the
  Blazar 3C 66A   The intermediate-frequency peaked BL Lacertae (IBL) object 3C 66A is detected
during 2007 - 2008 in VHE (very high energy: E > 100 GeV) gamma-rays with the
VERITAS stereoscopic array of imaging atmospheric Cherenkov telescopes. An
excess of 1791 events is detected, corresponding to a significance of 21.2
standard deviations (sigma), in these observations (32.8 hours live time). The
observed integral flux above 200 GeV is 6% of the Crab Nebula's flux and shows
evidence for variability on the time-scale of days. The measured energy
spectrum is characterized by a soft power law with photon index Gamma = 4.1 +-
0.4_stat +- 0.6_sys. The radio galaxy 3C 66B is excluded as a possible source
of the VHE emission.

24
The categories of this paper are: dg-ga
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
1
The categories of this paper are: cs
11
The categories of this paper are: hep-lat