Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Massive Stars in the SGR 1806-20 Cluster   We report the discovery of additional hot and massive stars in the cluster
surrounding the soft gamma repeater SGR 1806-20, based upon UKIRT and Keck
near-infrared spectroscopy. Of the newly identified stars, three are Wolf-Rayet
stars of types WC8, WN6, and WN7, and a fourth star is an OB supergiant. These
three stars, along with four previously discovered, imply a cluster age of
\~3.0-4.5 Myr, based on the presence of WC stars and the absence of red
supergiants. Assuming coevality, this age suggests that the progenitor of SGR
1806-20 had an initial mass greater than ~50 Msun. This is consistent with the
suggestion that SGRs are post-supernovae end states of massive progenitors, and
may suggest that only massive stars evolve into magnetars that produce SGRs. It
also suggests that very massive stars can evolve into neutron stars, not just
black holes, as recently predicted by theory. The cluster age also provides
constraints on the very high mass object, LBV 1806-20.

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The categories of this paper are: hep-ph
17
The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
3
The categories of this paper are: physics
35
The categories of this paper are: mtrl-th
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
25
The categories of this paper are: patt-sol
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The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
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The categories of this paper are: hep-ex