Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: X-ray binaries and their descendants: binary radio pulsars; evidence for
  three classes of neutron stars?   An important recent discovery by Pfahl et al. (2002) is that there are two
classes of Be X-ray binaries: one with orbits of small eccentricity (<0.25), in
which the neutron stars received hardly any kick velocity at birth and a class
with substantial orbital eccentricities, in which the neutron stars received a
kick velocity of order 100 km/s at birth. Also many of the double neutron stars
(5 out of 7) have a low orbital eccentricity (0.09 to 0.27), which indicates
that their second-born neutron stars received hardly any velocity kick at
birth. These second-born neutron stars tend to have low masses (1.25 to 1.35
Msun). It is proposed that the low-mass, low-kick neutron stars are formed by
the electron capture of degenerate O-Ne-Mg cores of stars with initial masses
below about 12-14 Msun, while the high-kick neutron stars originated from the
photo-disintegration collapse of the iron cores of stars which started out with
masses larger than this limit. The latter group may be further subdivided into
two classes of different mass.

25
The categories of this paper are: patt-sol
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
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The categories of this paper are: chao-dyn