J/A+A/645/A72 Radial velocities of UCAC4 721-037069 (Clavel+, 2021)
Using radial velocities to reveal black holes in binaries: A test case.
Clavel M., Dubus G., Casares J., Babusiaux C.
<Astron. Astrophys. 645, A72 (2021)>
=2021A&A...645A..72C 2021A&A...645A..72C (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, eclipsing ; Radial velocities
Keywords: stars: black holes - stars: individual: UCAC4 721-037069 -
X-rays: stars - binaries: eclipsing - techniques: radial velocities
Abstract:
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 that has a known X-ray counterpart (UCAC4 721-037069).
We obtained time-resolved spectra from the Liverpool Telescope and a
5 ks observation from the Chandra observatory to fully constrain the
orbital parameters and the X-ray emission of this system.
We find the source to be an eclipsing stellar binary that can be
classified as an 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
Using only radial velocity to identify black hole candidates can lead
to many false positives. The presence of an optical orbital
modulation, such as what has been observed for all LAMOST candidates,
will in most cases indicate that the system is a stellar binary.
Description:
Radial velocity measurements of UCAC4 721-037069 derived from
time-resolved spectra obtained by the Liverpool Telescope in 2019.
Objects:
-------------------------------------------------------------------------
RA (2000) DE Designation(s)
-------------------------------------------------------------------------
04 56 12.77 +54 00 21.3 UCAC4 721-037069 = Gaia DR2 273187064220377600
-------------------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
rv.dat 50 26 Radial velocity as a function of time
--------------------------------------------------------------------------------
Byte-by-byte Description of file: rv.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 F17.9 d HJD Observation date
25- 34 F10.6 km/s RV Radial velocity
42- 50 F9.7 km/s e_RV Radial Velocity Error
--------------------------------------------------------------------------------
Acknowledgements:
Maica Clavel, maica.clavel(at)univ-grenoble-alpes.fr
(End) Maica Clavel [IPAG, France], Patricia Vannier [CDS] 19-Nov-2020