Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Chandra observation of the most interesting cluster in the Universe   Chandra has recently observed 1E0657-56, a hot merging system at z=0.3 (the
``bullet'' cluster), for 500 ks. I present some of the findings from this
dataset. The cluster exhibits a prominent bow shock with M=3.0+-0.4 (one of
only two known M>>1 shock fronts), which we use for a first test of the
electron-ion equilibrium in an intergalactic plasma. The temperatures across
the shock are consistent with instant shock-heating of the electrons; at 95%
confidence, the equilibration timescale is much shorter than the collisional
Spitzer value. Global properties of 1E0657-56 are also remarkable. Despite
being extremely unrelaxed, the cluster fits well on the Lx-T relation, yet its
total mass estimated from the M-T relation is more than twice the value
measured from lensing. This is consistent with simulations predicting that in
the middle of a merger, global temperature and X-ray luminosity may be
temporarily boosted by a large factor.

10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
16
The categories of this paper are: stat
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
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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: math
32
The categories of this paper are: atom-ph
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The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an