Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Binary microlensing event OGLE-2009-BLG-020 gives a verifiable mass,
  distance and orbit predictions   We present the first example of binary microlensing for which the parameter
measurements can be verified (or contradicted) by future Doppler observations.
This test is made possible by a confluence of two relatively unusual
circumstances. First, the binary lens is bright enough (I=15.6) to permit
Doppler measurements. Second, we measure not only the usual 7 binary-lens
parameters, but also the 'microlens parallax' (which yields the binary mass)
and two components of the instantaneous orbital velocity. Thus we measure,
effectively, 6 'Kepler+1' parameters (two instantaneous positions, two
instantaneous velocities, the binary total mass, and the mass ratio). Since
Doppler observations of the brighter binary component determine 5 Kepler
parameters (period, velocity amplitude, eccentricity, phase, and position of
periapsis), while the same spectroscopy yields the mass of the primary, the
combined Doppler + microlensing observations would be overconstrained by 6 + (5
+ 1) - (7 + 1) = 4 degrees of freedom. This makes possible an extremely strong
test of the microlensing solution. We also introduce a uniform microlensing
notation for single and binary lenses, we define conventions, summarize all
known microlensing degeneracies and extend a set of parameters to describe full
Keplerian motion of the binary lenses.

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The categories of this paper are: hep-ex
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The categories of this paper are: cond-mat
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The categories of this paper are: eess
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The categories of this paper are: gr-qc
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The categories of this paper are: q-fin
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The categories of this paper are: cs
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The categories of this paper are: nucl-ex
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The categories of this paper are: funct-an
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The categories of this paper are: nlin
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The categories of this paper are: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: physics
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The categories of this paper are: chao-dyn
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The categories of this paper are: math-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga