HR 6819 is a binary system with no black hole -- revisiting the source with infrared interferometry and optical integral field spectroscopy

Abstract

Two scenarios have been proposed to match the existing observational constraints of the object HR 6819. The system could consist of a close inner B-type giant plus a black hole (BH) binary with an additional Be companion in a wide orbit. Alternatively, it could be a binary composed of a stripped B star and a Be star in a close orbit. Either scenario makes HR 6819 a cornerstone object as the stellar BH closest to Earth, or as an example of an important transitional, non-equilibrium phase for Be stars with solid evidence for its nature. We aimed to distinguish between the two scenarios for HR 6819. Both models predict two luminous stars but with very different angular separations and orbital motions. Therefore, the presence of bright sources in the 1-100 milliarcsec (mas) regime is a key diagnostic for determining the nature of the HR 6819 system. We obtained new high-angular resolution data with VLT/MUSE and VLTI/GRAVITY of HR 6819. The MUSE data are sensitive to bright companions at large scales, whilst the interferometric GRAVITY data are sensitive down to separations on mas scales and large magnitude differences. The MUSE observations reveal no bright companion at large separations and the GRAVITY observations indicate the presence of a stellar companion at an angular separation of ~1.2 mas that moves on the plane of the sky over a timescale compatible with the known spectroscopic 40-day period. We conclude that HR 6819 is a binary system and that no BH is present in the system. The unique nature of HR 6819, and its proximity to Earth make it an ideal system for quantitatively characterising the immediate outcome of binary interaction and probing how Be stars form.

16 pages, 11 figures, subject of ESO press release eso2204

References in corpus (20)

• Binary interaction dominates the evolution of massive stars
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• Catalogue of high-mass X-ray binaries in the Galaxy ($4^{th}$ edition)
• The Data Processing Pipeline for the MUSE Instrument
• The Tarantula Massive Binary Monitoring: I. Observational campaign and OB-type spectroscopic binaries
• Is HR 6819 a triple system containing a black hole? -- An alternative explanation
• Near-Infrared interferometry of Eta Carinae with high spatial and spectral resolution using the VLTI and the AMBER instrument
• A naked-eye triple system with a nonaccreting black hole in the inner binary
• Investigating the lack of main-sequence companions to massive Be stars
• Not so fast: LB-1 is unlikely to contain a 70 $M_{\odot }$ black hole
• The Tarantula Massive Binary Monitoring: III. Atmosphere analysis of double-lined spectroscopic systems
• A stripped helium star in the potential black hole binary LB-1
• The Tarantula Massive Binary Monitoring. IV. Double-lined photometric binaries
• gamma Cas stars: Normal Be stars with disks impacted by the wind of a helium-star companion?
• The B-type Binaries Characterisation Programme I. Orbital solutions for the 30 Doradus population
• A detailed non-LTE analysis of LB-1: Revised parameters and surface abundances
• Impact of initial mass functions on the dynamical channel of gravitational wave sources
• The H-alpha Emission Line Variations of HR 6819
• Resolving the dynamical mass tension of the massive binary 9 Sagittarii
• The nearest discovered black hole is likely not in a triple configuration

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• Formation and Destiny of White Dwarf and Be Star Binaries
• Characterising the orbit and circumstellar environment of the high-mass binary MWC 166 A