Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fermi LAT Observations of Supernova Remnants Interacting with Molecular
  Clouds   We report the detection of gamma-ray emission coincident with four supernova
remnants (SNRs) using data from the Large Area Telescope on board the Fermi
Gamma-ray Space Telescope. G349.7+0.2, CTB 37A, 3C 391 and G8.7-0.1 are
supernova remnants known to be interacting with molecular clouds, as evidenced
by observations of hydroxyl (OH) maser emission at 1720 MHz in their
directions. SNR shocks are expected to be sites of cosmic rays acceleration,
and clouds of dense material can provide effective targets for production of
gamma-rays from pion-decay. The observations reveal unresolved sources in the
direction of G349.7+0.2, CTB 37A and 3C 391, and a possibly extended source
coincident with G8.7-0.1, all with significance levels greater than 10 sigma.

1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
34
The categories of this paper are: chem-ph
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics