Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spatial and velocity coincidence of 4765- and 1720-MHz OH masers in two
  star-forming regions Cep A and W75N   We present the first maps of 4765-MHz OH masers in two star-forming regions
Cepheus A and W75N, made with Multi-Element Radio Linked Interferometer
Network. In Cep A the emission has an arc-like structure of size 40 mas with a
clear velocity gradient, and lies at the edge of H II region 3b Over a period
of 8 weeks the maser diminished in intensity by a factor of 7 but its structure
remained stable. This structure coincides with a newly mapped 1720-MHz maser in
Cep A within the positional error, and matches it in velocity. The 1720-MHz
line exhibits Zeeman splitting that corresponds to a magnetic field strength of
-17.3 mG. In W75N the excited 4765-MHz OH maser has a linear structure of size
45 mas with a well defined velocity gradient, and lies at the edge of H II
region VLA 1. This structure coincides in position and velocity with the
1720-MHz masers. We conclude that in both sources the 4765-MHz emission
coexists with 1720-MHz emission in the same volume of gas. In such a case the
physical conditions in these regions are tightly constrained by the
maser-pumping models.

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The categories of this paper are: eess
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The categories of this paper are: cmp-lg
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The categories of this paper are: quant-ph
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The categories of this paper are: physics
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The categories of this paper are: math
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The categories of this paper are: hep-th
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: comp-gas
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The categories of this paper are: dg-ga
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The categories of this paper are: chem-ph
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The categories of this paper are: supr-con
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The categories of this paper are: adap-org
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The categories of this paper are: plasm-ph
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The categories of this paper are: econ
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The categories of this paper are: q-fin