Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Optical Gravitational Lensing Experiment. OGLE #7: Binary Microlens
  or a New Unusual Variable?   We present the light curve of an unusual variable object, OGLE #7, detected
during the OGLE search for microlensing events. After one season of being in a
low, normal state, the star brightened by more than 2~mag with a characteristic
double-maximum shape, and returned to normal brightness after 60 days. We
consider possible explanations of the photometric behavior of OGLE #7. The
binary microlens model seems to be the most likely explanation -- it reproduces
well the observed light curve and explains the observed colors of OGLE #7. The
characteristic time scale of the OGLE #7 event, $t_E$, is equal to 80 days, the
longest observed to date. The binary microlens model predicts that the spectrum
of the star should be composite, with roughly 50% of its light in the $I$-band
coming from a non-lensed source.

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The categories of this paper are: acc-phys
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The categories of this paper are: cond-mat
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The categories of this paper are: econ
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: nlin
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The categories of this paper are: supr-con
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The categories of this paper are: cs
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The categories of this paper are: comp-gas
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The categories of this paper are: math-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: quant-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: q-fin
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The categories of this paper are: q-alg