Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spitzer/MIPS 24 micron Observations of HD 209458b: 3 eclipses, 2.5
  transits, and a Phase Curve Corrupted by Instrumental Sensitivity Variations   We report the results of an analysis of all Spitzer/MIPS 24 micron
observations of HD 209458b, one of the touchstone objects in the study of
irradiated giant planet atmospheres. Altogether we analyze 2.5 transits, 3
eclipses, and a 58-hour near-continuous observation designed to detect the
planet's thermal phase curve. The results of our analysis are: (1) A mean
transit depth of 1.484% +/- 0.035%, consistent with previous measurements and
showing no evidence of variability in transit depth at the 3% level. (2) A mean
eclipse depth of 0.332% +/- 0.026%, somewhat higher than that previously
reported for this system; this new value brings observations into better
agreement with models. The dayside flux shows no evidence of variability at the
12% level. (3) Eclipses in the system occur 32 s +/- 129 s earlier than would
be expected from a circular orbit, which constrains the orbital quantity (e cos
omega) to be 0.00004 +/- 0.00033. This result is fully consistent with a
circular orbit and sets an upper limit of 140 m/s (3 sigma) on any
eccentricity-induced velocity offset during transit. The phase curve
observations (including one of the transits) exhibit an anomalous trend similar
to the detector ramp seen in previous Spitzer/IRAC observations; by modeling
this ramp we recover the system parameters. The photometry which follows the
ramp and transit exhibits a gradual, ~0.2% decrease in flux, similar to that
seen in pre-launch calibration data. The large uncertainties associated with
this poorly-understood, likely instrumental effect prevent us from usefully
constraining the planet's thermal phase curve. Our observations highlight the
need for a thorough understanding of detector-related instrumental effects on
long time scales when making the high-precision mid-infrared measurements
planned for future missions such as EChO, SPICA, and JWST. [abridged]

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The categories of this paper are: physics
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The categories of this paper are: hep-ex
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The categories of this paper are: q-bio
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The categories of this paper are: cond-mat
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The categories of this paper are: funct-an
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The categories of this paper are: q-alg
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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: plasm-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: stat
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The categories of this paper are: gr-qc
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The categories of this paper are: mtrl-th
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The categories of this paper are: adap-org
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The categories of this paper are: acc-phys
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The categories of this paper are: eess