Using radial velocities to reveal black holes in binaries: a test case

Abstract

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.

arXiv comment6 pages, 3 figures, Accepted for publication in Astronomy & Astrophysics

References in corpus (43)

• emcee: The MCMC Hammer
• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• On the Absorption of X-rays in the Interstellar Medium
• The Man Behind the Curtain: X-rays Drive the UV through NIR Variability in the 2013 AGN Outburst in NGC 2617
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• The Relation Between Optical Extinction and Hydrogen Column Density in the Galaxy
• Galactic Reddening in 3D from Stellar Photometry - An Improved Map
• BlackCAT: A catalogue of stellar-mass black holes in X-ray transients
• Gaia-2MASS 3D maps of Galactic interstellar dust within 3 kpc
• The disc instability model for X-ray transients: evidence for truncation and irradiation
• On the formation and evolution of black-hole binaries
• Discovery of a Candidate Black Hole - Giant Star Binary System in the Galactic Field
• High-Mass X-ray Binaries in the Milky Way: A closer look with INTEGRAL
• A detached stellar-mass black hole candidate in the globular cluster NGC 3201
• A Be-type star with a black hole companion
• A wide star-black-hole binary system from radial-velocity measurements
• A stellar census in globular clusters with MUSE: Binaries in NGC 3201
• Complete and Simultaneous Spectral Observations of the Black-Hole X-ray Nova XTE J1118+480
• The 'hidden' companion in LB-1 unveiled by spectral disentangling
• Is HR 6819 a triple system containing a black hole? -- An alternative explanation
• A naked-eye triple system with a nonaccreting black hole in the inner binary
• A study of X-ray flares - II. RS CVn type Binaries
• Synthetic catalog of black holes in the Milky Way
• The origin and fate of short-period low-mass black-hole binaries
• Physics of Eclipsing Binaries. IV. The impact of interstellar extinction on the light curves of eclipsing binaries
• X-ray outbursts of low-mass X-ray binary transients observed in the RXTE era
• The faintest accretors
• A stripped helium star in the potential black hole binary LB-1
• A fully automated data reduction pipeline for the FRODOSpec integral field spectrograph
• The origin of pulsating ultra-luminous X-ray sources: Low- and intermediate-mass X-ray binaries containing neutron star accretors
• Population Synthesis of Black Hole Binaries with Normal-Star Companions: I. Detached Systems
• A Population of Faint Non-Transient Low Mass Black Hole Binaries
• Comment on "A non-interacting low-mass black hole -- giant star binary system"
• Non-interacting black hole binaries with Gaia and LAMOST
• A Method to Search for Black Hole Candidates with Giant Companions by LAMOST
• The Million Optical - Radio/X-ray Associations (MORX) Catalogue
• Mining for Candidates of Galactic Stellar-mass Black Hole Binaries with LAMOST
• Searching for Black Hole Candidates by LAMOST and ASAS-SN
• Response to Comment on "A Non-Interacting Low-Mass Black Hole -- Giant Star Binary System"
• The nearest discovered black hole is likely not in a triple configuration
• Observations of red giants with suspected massive companions

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• Gaia Data Release 3: Ellipsoidal Variables with Possible Black-Hole or Neutron Star secondaries
• Minute-cadence Observations of the LAMOST Fields with the TMTS: I. Methodology of Detecting Short-period Variables and Results from the first-year Survey
• Spectroscopic follow-up of black hole and neutron star candidates in ellipsoidal variables from Gaia DR3