Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Detection of DCO+ in a circumstellar disk   We report the first detection of DCO+ in a circumstellar disk. The DCO+ J=5-4
line at 360.169 GHz is observed with the 15m James Clerk Maxwell Telescope in
the disk around the pre-main sequence star TW Hya. Together with measurements
of the HCO+ and H13CO+ J=4-3 lines, this allows an accurate determination of
the DCO+/HCO+ ratio in this disk. The inferred value of 0.035+-0.015 is close
to that found in cold pre-stellar cores and is somewhat higher than that
measured in the envelope around the low-mass protostar IRAS 16293 -2422. It is
also close to the DCN/HCN ratio obtained for pristine cometary material in the
jet of comet Hale-Bopp. The observed DCO+/HCO+ ratio for TW Hya is consistent
with theoretical models of disks which consider gas-phase fractionation
processes within a realistic 2-D temperature distribution and which include the
effects of freeze-out onto grains.

12
The categories of this paper are: nucl-th
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The categories of this paper are: math-ph
19
The categories of this paper are: eess
15
The categories of this paper are: nucl-ex
3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
0
The categories of this paper are: hep-ph
18
The categories of this paper are: econ
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
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The categories of this paper are: q-fin
9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn