Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gamma-Ray Bursts: Old and New   Gamma-ray bursts are sudden releases of energy that for a duration of a few
seconds outshine even huge galaxies. 30 years after the first detection of a
gamma-ray burst their origin remains a mystery. Here I first review the ``old''
problems which have baffled astronomers over decades, and then report on the
``new'' exciting discoveries of afterglow emission at longer wavelengths which
have raised more new questions than answered old ones.

28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
4
The categories of this paper are: cond-mat
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin