Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Long-term study of the Double Pulsar J0737-3039 with XMM-Newton:
  spectral analysis   We present a long-term spectral monitoring of the unique Double Pulsar binary
PSR J0737-3039 corresponding to two "Large Programs" performed by XMM-Newton in
2006 and 2011. Spectral variability of pulsar emission in soft X-rays is not
evident over 5 years, despite the significant relativistic spin precession in
the considered time span (about 25deg). We provide, for the first time,
evidence of hard X-ray emission from the system in the 5-8 keV energy band. The
standard spectral analysis was coupled to the energy dependent spatial analysis
to confirm this excess, most likely ascribed to iron line emission. The Fe
K-alpha emission line at 6.4-6.97 keV was previously unheard-of in
non-accreting binary systems and could testify to the presence of a relic disk
that survived the supernova explosions that terminated the lives of the Double
Pulsar's stellar progenitors. The existence of a relic disk in this system
reinforces speculation about the presence of similar structures around other
peculiar classes of isolated neutron stars.

11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
3
The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
28
The categories of this paper are: alg-geom
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc
4
The categories of this paper are: cond-mat
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess