Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Trigonometric Parallax of Cygnus X-1   We report a direct and accurate measurement of the distance to the X-ray
binary Cygnus X-1, which contains the first black hole to be discovered. The
distance of 1.86 (-0.11,+0.12) kpc was obtained from a trigonometric parallax
measurement using the Very Long Baseline Array. The position measurements are
also sensitive to the 5.6 d binary orbit and we determine the orbit to be
clockwise on the sky. We also measured the proper motion of Cygnus X-1 which,
when coupled to the distance and Doppler shift, gives the three-dimensional
space motion of the system. When corrected for differential Galactic rotation,
the non-circular (peculiar) motion of the binary is only about 21 km/s,
indicating that the binary did not experience a large "kick" at formation.

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The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
14
The categories of this paper are: math-ph
7
The categories of this paper are: hep-th
3
The categories of this paper are: physics
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
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The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
5
The categories of this paper are: gr-qc
10
The categories of this paper are: q-bio