Tiny newfound 'Unicorn' is closest known black hole to Earth

Interesting report. Here is another link on the black hole. https://ui.adsabs.harvard.edu/abs/2021arXiv210102212J/abstract, January 2021. "A Unicorn in Monoceros: the 3M⊙ dark companion to the bright, nearby red giant V723 Mon is a non-interacting, mass-gap black hole candidate..."We report the discovery of the closest known black hole candidate as a binary companion to V723 Mon. V723 Mon is a nearby ( d∼460pc ), bright ( V≃8.3 ~mag), evolved ( Teff,giant≃4440 ~K, and Lgiant≃173 L⊙ ) red giant in a high mass function, f(M)=1.72±0.01 M⊙ , nearly circular binary ( P=59.9 d, e≃0 ). V723 Mon is a known variable star, previously classified as an eclipsing binary, but its All-Sky Automated Survey (ASAS), Kilodegree Extremely Little Telescope (KELT), and Transiting Exoplanet Survey Satellite (TESS) light curves are those of a nearly edge-on ellipsoidal variable..."

The orbital period for the binary is 59.9 days. At 3 solar masses, Schwarzschild radius = 8.86 km, 17.72 km diameter. The system has a 1.72 solar mass red giant and 3 solar mass BH. V723 in Mon reported at 8.3 apparent magnitude. A red giant star visible in small telescopes. The abstract shows the calculation reduces the red giant mass to about 1 solar mass.