Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gas and dust in the TW Hydrae Association as seen by the Herschel Space
  Observatory   Context. Circumstellar discs are the places where planets form, therefore
knowledge of their evolution is crucial for our understanding of planet
formation. The Herschel Space Observatory is providing valuable data for
studying disc systems, thanks to its sensitivity and wavelength coverage. This
paper is one of several devoted to analysing and modelling Herschel-PACS
observations of various young stellar associations from the GASPS Open Time Key
Programme. Aims. The aim of this paper is to elucidate the gas and dust
properties of circumstellar discs in the 10 Myr TW Hya Association (TWA) using
new far-infrared (IR) imaging and spectroscopy from Herschel-PACS. Methods. We
obtained far-IR photometric data at 70, 100, and 160 microns of 14 TWA members;
spectroscopic observations centred on the [OI] line at 63.18 microns were also
obtained for 9 of the 14. The new photometry for each star was incorporated
into its full spectral energy distribution (SED). Results. We detected excess
IR emission that is characteristic of circumstellar discs from five TWA
members, and computed upper limits for another nine. Two TWA members (TWA 01
and TWA 04B) also show [OI] emission at 63.18 microns. Discs in the TWA
association display a variety of properties, with a wide range of dust masses
and inner radii, based on modified blackbody modelling. Both transitional and
debris discs are found in the sample. Models for sources with a detected IR
excess give dust masses in the range from 0.15 Msun to 63 Msun.

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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: econ
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The categories of this paper are: hep-ph
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The categories of this paper are: stat
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The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-bio
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The categories of this paper are: hep-lat
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The categories of this paper are: cs
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: cond-mat
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The categories of this paper are: supr-con
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The categories of this paper are: quant-ph