Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: INTEGRAL and XMM-Newton observations of LSI +61 303   LSI +61 303 is one of the few X-ray binaries with Be star companion from
which both radio and high-energy gamma-ray emission have been observed. We
present XMM-Newton and INTEGRAL observations which reveal variability of the
X-ray spectral index of the system. The X-ray spectrum is hard (photon index ~
1.5) during the orbital phases of both high and low X-ray flux. However, the
spectrum softens at the moment of transition from high to low X-ray state. The
spectrum of the system in the hard X-ray band does not reveal the presence of a
cut-off (or, at least a spectral break) at 10-60 keV energies, expected if the
compact object is an accreting neutron star. The observed spectrum and spectral
variability can be explained if the compact object in the system is a rotation
powered pulsar.

22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
14
The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph