LB-1 is inconsistent with the X-ray source population and pulsar-black hole binary searches in the Milky Way

Understand

If confirmed, a wide binary system of 70 $M_{\odot}$ black hole (BH) and an 8 $M_{\odot}$ main sequence star (LB-1) is observed to reside in the Milky Way (MW).

• We show that long term evolution of an 8 $M_{\odot}$ star around a BH with mass between 5-70 $M_{\odot}$ makes them visible as ultra-luminous X-ray (ULX) sources in the sky.
• Given the expected ULX phase lifetime ($\approx0.1$ Myr) and their lack of detection in the MW, we conclude that the frequency of an 8-20 $M_{\odot}$ star to be in binary around a stellar mass BH should be less than ($f<2\times10^{-3}$).
• This is in tension with Liu et al.