Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An upper bound on the energy of a gravitationally redshifted
  electron-positron annihilation line from the Crab pulsar   The various changes in the `abstract' are mentioned in point (1) of the
present erratum.

5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
16
The categories of this paper are: stat
1
The categories of this paper are: cs