Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: HD 100453: A Link Between Gas-Rich Protoplanetary Disks and Gas-Poor
  Debris Disks   HD 100453 has an IR spectral energy distribution (SED) which can be fit with
a power-law plus a blackbody. Previous analysis of the SED suggests that the
system is a young Herbig Ae star with a gas-rich, flared disk. We reexamine the
evolutionary state of the HD 100453 system by refining its age (based on a
candidate low-mass companion) and by examining limits on the disk extent, mass
accretion rate, and gas content of the disk environment. We confirm that HD
100453B is a common proper motion companion to HD 100453A, with a spectral type
of M4.0V - M4.5V, and derive an age of 10 +/- 2 Myr. We find no evidence of
mass accretion onto the star. Chandra ACIS-S imagery shows that the Herbig Ae
star has L_X/L_Bol and an X-ray spectrum similar to non-accreting Beta Pic
Moving Group early F stars. Moreover, the disk lacks the conspicuous Fe II
emission and excess FUV continuum seen in spectra of actively accreting Herbig
Ae stars, and from the FUV continuum, we find the accretion rate is < 1.4x10^-9
M_Sun yr^-1. A sensitive upper limit to the CO J = 3-2 intensity indicates that
the gas in the outer disk is likely optically thin. Assuming a [CO]/[H2]
abundance of 1x10^-4 and a depletion factor of 10^3, we find that the mass of
cold molecular gas is less than ~0.33 M_J and that the gas-to-dust ratio is no
more than ~4:1 in the outer disk. The combination of a high fractional IR
excess luminosity, a relatively old age, an absence of accretion signatures,
and an absence of detectable circumstellar molecular gas suggests that the HD
100453 system is in an unusual state of evolution between a gas-rich
protoplanetary disk and a gas-poor debris disk.

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The categories of this paper are: nucl-th
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The categories of this paper are: solv-int
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The categories of this paper are: stat
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The categories of this paper are: atom-ph
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The categories of this paper are: math
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The categories of this paper are: alg-geom
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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: hep-lat
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The categories of this paper are: comp-gas
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-ph
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The categories of this paper are: q-alg
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The categories of this paper are: q-bio
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The categories of this paper are: supr-con