Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Time-Delay Measurement for the Quadruple Lens RX J1131-1231   We have measured the three time delays for the quadruple gravitational lens
RX J1131-1231 using two seasons of monitoring data. The short delays between
cusp images are A-B = 11.98 +1.52,-1.27 days and A-C = 9.61 +1.97,-1.57 days.
The long A-D delay for the counter image is not as precisely determined because
of the season gaps, but the data suggest a delay of -87 +- 8 days. The short
delays are difficult to explain using standard isothermal halo models of the
lensing potential, which instead prefer A-B and A-C delays of ~1 day for
reasonable values of the Hubble constant. Matching the cusp delays is possible
by adding a significant (~5 x 10^10 M_sun) amount of matter nearly coincident
(~0.05" South-East) with the A image. Adding such a satellite also helps
improve the quasar and lens astrometry of the model, reduces the velocity
dispersion of the main lens and shifts it closer to the Fundamental Plane. This
is suggestive of a satellite galaxy to the primary lens, but its expected
luminosity and proximity to both image A and the system's bright Einstein ring
make visual identification impossible even with the existing HST data. We also
find evidence for significant structure along the line of sight toward the
lens. Archival Chandra observations show two nearby regions of extended X-ray
emission, each with bolometric X-ray luminosities of 2-3 x 10^43 ergs/s. The
brighter region is located 153" from the lens and centered on a z=0.1
foreground cD galaxy, and the fainter and presumably more distant region is 4-5
times closer (in angular separation) to the lens and likely corresponds to the
weaker of two galaxy red sequences (which includes the lens galaxy) previously
detected at optical wavelengths.

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The categories of this paper are: comp-gas
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The categories of this paper are: bayes-an
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The categories of this paper are: quant-ph
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The categories of this paper are: nlin
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The categories of this paper are: q-bio
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The categories of this paper are: dg-ga
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The categories of this paper are: mtrl-th
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The categories of this paper are: math
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The categories of this paper are: nucl-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: chem-ph
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The categories of this paper are: cs
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The categories of this paper are: math-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: ao-sci
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The categories of this paper are: physics