Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Discovery of an Optically Thick, Edge-on Disk around the Herbig Ae star
  PDS 144N   We have discovered an optically thick, edge-on circumstellar disk around a
Herbig Ae star in the binary system PDS 144, providing the first
intermediate-mass analog of HK Tau and similar T Tauris. This system consists
of a V ~ 13 mag. primary and a fainter companion, with spectra of both stars
showing evidence for circumstellar disks and accretion; both stars were
classified as Herbig Aes by the Pico dos Dias survey. In Lick adaptive optics
polarimetry, we resolved extended polarized light scattered from dust around
the northern star. Followup Keck adaptive optics and mid-infrared observations
show that this star is entirely hidden by an optically thick disk at all
wavelengths from 1.2 to 11.7 microns. The disk major axis subtends ~ 0.8" on
the sky, corresponding to ~ 800 AU at a distance of 1000 pc. Bright "wings"
extend 0.3" above and below the disk ansae, due most likely to scattering from
the edges of an outflow cavity in a circumstellar envelope. We discuss the
morphology of the disk and the spectral energy distributions of the two PDS 144
stars, present preliminary disk models, and identify a number of open questions
regarding this fascinating system.

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The categories of this paper are: patt-sol
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The categories of this paper are: funct-an
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The categories of this paper are: stat
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The categories of this paper are: ao-sci
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The categories of this paper are: supr-con
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The categories of this paper are: q-fin
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The categories of this paper are: solv-int
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: physics
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The categories of this paper are: quant-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: atom-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: eess