Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence of an asteroid encountering a pulsar   Debris disks and asteroid belts are expected to form around young pulsars due
to fallback material from their original supernova explosions. Disk material
may migrate inwards and interact with a pulsar's magnetosphere, causing changes
in torque and emission. Long term monitoring of PSR J0738-4042 reveals both
effects. The pulse shape changes multiple times between 1988 and 2012. The
torque, inferred via the derivative of the rotational period, changes abruptly
from September 2005. This change is accompanied by an emergent radio component
that drifts with respect to the rest of the pulse. No known intrinsic pulsar
processes can explain these timing and radio emission signatures. The data lead
us to postulate that we are witnessing an encounter with an asteroid or
in-falling debris from a disk.

27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
28
The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph
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The categories of this paper are: quant-ph
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
2
The categories of this paper are: math
14
The categories of this paper are: math-ph
7
The categories of this paper are: hep-th
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The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga