Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Using radial velocities to reveal black holes in binaries: a test case   Aims. Large radial velocity variations in the LAMOST spectra of giant stars
have been used to infer the presence of unseen companions. Some of them have
been proposed as possible black hole candidates. We test this selection by
investigating the classification of the one candidate having a known X-ray
counterpart (UCAC4 721-037069). Methods. We obtained time-resolved spectra from
the Liverpool Telescope and a 5ks observation from the Chandra observatory to
fully constrain the orbital parameters and the X-ray emission of this system.
Results. We find the source to be an eclipsing stellar binary that can be
classified as a RS CVn. The giant star fills its Roche Lobe and the binary mass
ratio is greater than one. The system may be an example of stable mass transfer
from an intermediate-mass star with a convective envelope. Conclusions. Using
only radial velocity to identify black hole candidates can lead to many false
positives. The presence of an optical orbital modulation, such as observed for
all LAMOST candidates, will in most cases indicate that this is a stellar
binary.

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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: q-bio
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The categories of this paper are: nlin
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The categories of this paper are: acc-phys
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The categories of this paper are: adap-org
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The categories of this paper are: stat
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The categories of this paper are: gr-qc
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The categories of this paper are: chao-dyn
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The categories of this paper are: math-ph
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The categories of this paper are: eess
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: funct-an
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The categories of this paper are: q-fin