  The detection of a sub-solar mass black hole could yield dramatic new
insights into the nature of dark matter and early-Universe physics, as such
objects lack a traditional astrophysical formation mechanism. Gravitational
waves allow for the direct measurement of compact object masses during binary
mergers, and we expect the gravitational-wave signal from a low-mass
coalescence to remain within the LIGO frequency band for thousands of seconds.
However, it is unclear whether one can confidently measure the properties of a
sub-solar mass compact object and distinguish between a sub-solar mass black
hole or other exotic objects. To this end, we perform Bayesian parameter
estimation on simulated gravitational-wave signals from sub-solar mass black
hole mergers to explore the measurability of their source properties. We find
that the LIGO/Virgo detectors during the O4 observing run would be able to
confidently identify sub-solar component masses at the threshold of
detectability; these events would also be well-localized on the sky and may
reveal some information on their binary spin geometry. Further, next-generation
detectors such as Cosmic Explorer and the Einstein Telescope will allow for
precision measurement of the properties of sub-solar mass mergers and tighter
constraints on their compact-object nature.
