A naked-eye triple system with a nonaccreting black hole in the inner binary

0536815 - ASÚ 2021 RIV FR eng J - Journal Article
Rivinius, T. - Baade, D. - Hadrava, Petr - Heida, M. - Klement, R.
A naked-eye triple system with a nonaccreting black hole in the inner binary.
Astronomy & Astrophysics. Roč. 637, May (2020), č. článku L3. ISSN 0004-6361. E-ISSN 1432-0746
Institutional support: RVO:67985815
Keywords : stars * black holes * spectroscopic
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 5.803, year: 2020
Method of publishing: Limited access
https://doi.org/10.1051/0004-6361/202038020

Several dozen optical echelle spectra demonstrate that HR 6819 is a hierarchical triple. A classical Be star is in a wide orbit with an unconstrained period around an inner 40 d binary consisting of a B3 III star and an unseen companion in a circular orbit. The radial-velocity semi-amplitude of 61.3 km s(-1) of the inner star and its minimum (probable) mass of 5.0 M-circle dot (6.3 +/- 0.7 M-circle dot) imply a mass of the unseen object of >= 4.2 M-circle dot (>= 5.0 +/- 0.4 M-circle dot), that is, a black hole (BH). The spectroscopic time series is stunningly similar to observations of LB-1. A similar triple-star architecture of LB-1 would reduce the mass of the BH in LB-1 from similar to 70 M-circle dot to a level more typical of Galactic stellar remnant BHs. The BH in HR 6819 probably is the closest known BH to the Sun, and together with LB-1, suggests a population of quiet BHs. Its embedment in a hierarchical triple structure may be of interest for models of merging double BHs or BH + neutron star binaries. Other triple stars with an outer Be star but without BH are identified - through stripping, such systems may become a source of single Be stars.
Permanent Link: http://hdl.handle.net/11104/0314565