Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Analysis of the OGLE microlensing candidates using the image subtraction
  method   The light curves of the OGLE microlensing candidates have been reconstructed
using the image subtraction method. A large improvement of the photometric
accuracy has been found in comparison with previous processing of the data with
DoPHOT. On the mean, the residuals to the fit of a microlensing light curve are
improved by a factor of 2 for baseline data points, and by a factor of 2.5
during magnification. The largest improvement was found for the OGLE #5 event,
where we get an accuracy 7.5 times better than with DoPHOT. Despite some
defects in the old CCD used during the OGLE I experiment we obtain most of the
time errors that are only 30 % to 40 % in excess of the photon noise. Previous
experiment showed that with modern CCD chips (OGLE II), residuals much closer
to the photon noise were obtained. The better photometric quality enabled us to
find a low amplitude, long term variability in the OGLE #12 and OGLE #11
baseline magnitude. We also found that the shape of the OGLE #14 candidate
light curve is fairly inconsistent with microlensing of a point source by a
point lens. A dramatic change in the light curve of the OGLE #9 candidate was
also found, which indicates that very large biases can be present in data
processed with DoPHOT. To conclude we made a detailed analysis of the blending
issue. It is found that OGLE #5 and OGLE #6 are very likely highly blended
microlensing events. These events result from the magnification of a faint star
that would have been undetectable without microlensing.

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The categories of this paper are: q-alg
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The categories of this paper are: cmp-lg
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The categories of this paper are: math
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The categories of this paper are: atom-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: math-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-lat
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The categories of this paper are: econ
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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: dg-ga
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The categories of this paper are: nlin
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The categories of this paper are: nucl-ex
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The categories of this paper are: quant-ph