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Last week the
OzGrav Centre of Excellence
held their Annual Retreat,
which was preceded by the annoucement from the
LIGO and Virgo consortia of the detection of four
black hole mergers from a reprocessing of data
from the second run of the detectors in July and August 2017.
Two of the
notable features from these results are: (i)
While LIGO is sensitive to mergers of black holes
up to a few hundred solar masses, so far there
don't appear to get larger than about 50 solar masses,
suggesting that
black holes arising from
ultra-massive stars may be rare.
(ii)
The addition of the VIRGO detector to the two LIGO detectors
increased the detection rate significantly.
During the final month of observing, last year the event rate was more than one per week.
This indicates that the event rate for the next run, scheduled to start in March 2019,
is likely to be even higher.
The figure above shows the pre- and post-merger masses of the objects involved,
together with black hole and neutron star masses inferred from other observations.
(Credit: LIGO/Virgo, Frank Elavsky, Northwestern)
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