Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observation of Microlensing towards the Galactic Spiral Arms. EROS II 3
  year survey   We present an analysis of the light curves of 9.1 million stars observed
during three seasons by EROS (Experience de Recherche d'Objets Sombres), in the
Galactic plane away from the bulge. Seven stars exhibit luminosity variations
compatible with gravitational microlensing effects due to unseen objects. The
corresponding optical depth, averaged over four directions, is tau = 0.45 +0.24
-0.11 x 10^-6. While this value is compatible with expectations from simple
galactic models under reasonable assumptions on the target distances, we find
an excess of events with short timescale towards the direction closest to the
Galactic Centre.

18
The categories of this paper are: econ
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: nlin
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The categories of this paper are: hep-ex
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The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
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The categories of this paper are: funct-an
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The categories of this paper are: bayes-an