Weighing in on black hole binaries with BPASS: LB-1 does not contain a
  70M$_{\odot}$ black hole
  The recent identification of a candidate very massive 70 M(Sun) black hole is
at odds with our current understanding of stellar winds and pair-instability
supernovae. We investigate alternate explanations for this system by searching
the BPASS v2.2 stellar and population synthesis models for those that match the
observed properties of the system. We find binary evolution models that match
the LB-1 system, at the reported Gaia distance, with more moderate black hole
masses of 4 to 7 M(Sun). We also examine the suggestion that the binary motion
may have led to an incorrect distance determination by Gaia. We find that the
Gaia distance is accurate and that the binary system is consistent with the
observation at this distance. Consequently it is highly improbable that the
black hole in this system has the extreme mass originally suggested. Instead,
it is more likely to be representative of the typical black hole binary
population expected in our Galaxy.
