Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The state of protoplanetary material 10 Myr after stellar formation:
  circumstellar disks in the TW Hydrae association   We have used the Spitzer Infrared Spectrograph to observe seven members of
the TW Hya association, the nearest stellar association whose age ($\sim$ 10
Myr) is similar to the timescales thought to apply to planet formation and disk
dissipation. Only two of the seven targets display infrared excess emission,
indicating that substantial amounts of dust still exist closer to the stars
than is characteristic of debris disks; however, in both objects we confirm an
abrupt short-wavelength edge to the excess, as is seen in disks with
cleared-out central regions. The mid-infrared excesses in the spectra of Hen
3-600 and TW Hya include crystalline silicate emission features, indicating
that the grains have undergone significant thermal processing. We offer a
detailed comparison between the spectra of TW Hya and Hen 3-600, and a model
that corroborates the spectral shape and our previous understanding of the
radial structure of these protoplanetary disks.

17
The categories of this paper are: q-fin
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
16
The categories of this paper are: stat
4
The categories of this paper are: cond-mat
37
The categories of this paper are: supr-con
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex