English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Several dozen optical echelle spectra demonstrate that HR 6819 is ahierarchical triple. A classical Be star is in a wide orbit with anunconstrained period around an inner 40 d binary consisting of a B3 III starand an unseen companion in a circular orbit. The radial-velocity semi-amplitudeof 61.3 km/s of the inner star and its minimum (probable) mass of 5.0 Msun (6.3+- 0.7 Msun) imply a mass of the unseen object of >= 4.2 Msun (>= 5.0 +- 0.4Msun), that is, a black hole (BH). The spectroscopic time series is stunninglysimilar to observations of LB-1. A similar triple-star architecture of LB-1would reduce the mass of the BH in LB-1 from ~70 Msun to a level more typicalof Galactic stellar remnant BHs. The BH in HR 6819 probably is the closestknown BH to the Sun, and together with LB-1, suggests a population of quietBHs. Its embedment in a hierarchical triple structure may be of interest formodels of merging double BHs or BH + neutron star binaries. Other triple starswith an outer Be star but without BH are identified; through stripping, suchsystems may become a source of single Be stars.

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