Abstract:
The high-mass X-ray binary system Cygnus X-1 contains one of the first
known and best-studied black holes. We recently refined the distance
to the source using astrometric very long baseline interferometry
observations. The new distance implied that the component masses
needed to be revised upwards, with our modelling showing that the
system hosts a 21-solar mass black hole. The formation of such a
massive black hole in a Galactic environment with roughly solar
metallicity challenges existing model prescriptions for the wind mass
loss rates from massive stars. I will discuss our new measurements
and their consequences for the likely formation and subsequent
evolutionary pathway of the black hole, and touch on their
implications for massive star evolution and the formation of
gravitational-wave sources. (Image credit: ICRAR)
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