Reinterpreting Low Frequency LIGO/Virgo Events as Magnified Stellar-Mass
  Black Holes at Cosmological Distances
  Gravitational waves can be focussed by the gravity of an intervening galaxy,
just like light, thereby magnifying binary merging events in the far Universe.
High magnification by galaxies is found to be responsible for the brightest
sources detected in sky surveys, but the low angular resolution of LIGO/Virgo
is insufficient to check this lensing possibility directly. Here we find that
the first six binary black hole (BBH) merging events reported by LIGO/Virgo
show clear evidence for lensing in the plane of observed mass and source
distance. The four lowest frequency events follow an apparent locus in this
plane, which we can reproduce by galaxy lensing, where the higher the
magnification, the generally more distant the source so the wave train is
stretched more by the Universal expansion, by factors of 2-4. This revises the
reported BBH distances upwards by an order of magnitude, equal to the square
root of the magnification. Furthermore, the reported black hole masses must be
decreased by 2-4 to counter the larger stretch factor, since the orbital
frequency is used to derive the black hole masses. This lowers the masses to
5-15 solar masses, well below the puzzlingly high values of 20-35 solar masses
otherwise estimated, with the attraction of finding agreement in mass with
black holes orbiting stars in our own Galaxy, thereby implying a stellar origin
for the low frequency events in the far Universe. We also show that the other
two BBH events of higher frequency detected by LIGO/VIRGO, lie well below the
lensing locus, consistent with being nearby and unlensed. If this apparent
division between local and distant lensed events is reinforced by new
detections then the spins and masses of stellar black holes can be compared
over a timespan of 10 billion years by LIGO/Virgo.
