Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Discovery of an X-ray nebula around PSR J1718-3825 and implications for
  the nature of the gamma-ray source HESS J1718-385   Combined X-ray synchrotron and inverse-Compton gamma-ray observations of
pulsar wind nebulae (PWN) may help to elucidate the processes of acceleration
and energy loss in these systems. In particular, such observations provide
constraints on the particle injection history and the magnetic field strength
in these objects. The newly discovered TeV gamma-ray source HESS J1718-385 has
been proposed as the likely PWN of the high spin-down luminosity pulsar PSR
J1718-3825. The absence of previous sensitive X-ray measurements of this
pulsar, and the unusual energy spectrum of the TeV source, motivated
observations of this region with XMM-Newton. The data obtained reveal a hard
spectrum X-ray source at the position of PSR 1718-3825 and evidence for diffuse
emission in the vicinity of the pulsar. We derive limits on the keV emission
from the centroid of HESS J1718-385 and discuss the implications of these
findings for the PWN nature of this object.

10
The categories of this paper are: q-bio
2
The categories of this paper are: math
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
25
The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph
18
The categories of this paper are: econ
14
The categories of this paper are: math-ph
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
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The categories of this paper are: nucl-th