000006148 001__ 6148
000006148 005__ 20230123124336.0
000006148 0247_ $$2DOI$$a10.1051/0004-6361/202143004
000006148 037__ $$aSCART-2023-0074
000006148 100__ $$aFrost, A. J. 
000006148 245__ $$aHR 6819 is a binary system with no black hole. Revisiting the source with infrared interferometry and optical integral field spectroscopy
000006148 260__ $$c2022
000006148 520__ $$aContext. Two scenarios have been proposed to match the existing observational constraints of the object HR 6819. The system could consist of a close inner B-type giant plus a black hole (BH) binary with an additional Be companion in a wide orbit. Alternatively, it could be a binary composed of a stripped B star and a Be star in a close orbit. Either scenario makes HR 6819 a cornerstone object as the stellar BH closest to Earth, or as an example of an important transitional, non-equilibrium phase for Be stars with solid evidence for its nature. Aims. We aim to distinguish between the two scenarios for HR 6819. Both models predict two luminous stars but with very different angular separations and orbital motions. Therefore, the presence of bright sources in the 1−100 milliarcsec (mas) regime is a key diagnostic for determining the nature of the HR 6819 system. Methods. We obtained new high-angular resolution data with VLT/MUSE and VLTI/GRAVITY of HR 6819. The MUSE data are sensitive to bright companions at large scales, whilst the interferometric GRAVITY data are sensitive down to separations on mas scales and large magnitude differences. Results. The MUSE observations reveal no bright companion at large separations and the GRAVITY observations indicate the pres- ence of a stellar companion at an angular separation of ∼1.2 mas that moves on the plane of the sky over a timescale compatible with the known spectroscopic 40-day period. Conclusions. We conclude that HR 6819 is a binary system and that no BH is present in the system. The unique nature of HR 6819, and its proximity to Earth make it an ideal system for quantitatively characterising the immediate outcome of binary interaction and probing how Be stars form.
000006148 594__ $$aNO
000006148 6531_ $$astars:individual:HR6819
000006148 6531_ $$astars:massive
000006148 6531_ $$astars:emission-line,Be
000006148 6531_ $$abinaries:close
000006148 6531_ $$atechniques:interferometric
000006148 6531_ $$atechniques: imaging spectroscopy
000006148 700__ $$aBodensteiner, J.
000006148 700__ $$aRivinius, Th. 
000006148 700__ $$aBaade, D. 
000006148 700__ $$aMerand, A.  
000006148 700__ $$aSelman, F. 
000006148 700__ $$aAbdul-Masih, M. 
000006148 700__ $$aBanyard, G.
000006148 700__ $$aBordier, E.
000006148 700__ $$aDsilva, K. 
000006148 700__ $$aHawcroft, C. 
000006148 700__ $$aMahy, L.  
000006148 700__ $$aReggiani, M. 
000006148 700__ $$aShenar, T. 
000006148 700__ $$aCabezas, M.  
000006148 700__ $$aHadrava, P. 
000006148 700__ $$aHeida, M.
000006148 700__ $$aKlement, R. 
000006148 700__ $$aSana, H. 
000006148 773__ $$c12$$nL3$$pAstronomy & Astrophysics$$v659$$y2022
000006148 8560_ $$flaurent.mahy@ksb-orb.be
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000006148 905__ $$apublished in
000006148 980__ $$aREFERD