Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An Accretion Model for Anomalous X-Ray Pulsars   We present a model for the anomalous X-ray pulsars (AXPs) in which the
emission is powered by accretion from a fossil disk, established from matter
falling back onto the neutron star following its birth. The time-dependent
accretion drives the neutron star towards a ``tracking'' solution in which the
rotation period of the star increases slowly, in tandem with the declining
accretion rate. For appropriate choices of disk mass, neutron star magnetic
field strength and initial spin period, we demonstrate that a rapidly rotating
neutron star can be spun down to periods characteristic of AXPs on timescales
comparable to the estimated ages of these sources. In other cases, accretion
onto the neutron star switches off after a short time, and the star becomes an
ordinary radio pulsar. Thus, in our picture, radio pulsars and AXPs are drawn
from the same underlying population, in contrast to models involving neutron
stars with ultrastrong magnetic fields, which require a new population of stars
with very different properties.

26
The categories of this paper are: bayes-an
8
The categories of this paper are: hep-ex
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
22
The categories of this paper are: chao-dyn
32
The categories of this paper are: atom-ph
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc