Test for the Origin of Solar Mass Black Holes
  Solar-mass black holes with masses in the range of $\sim 1-2.5 M_{\odot}$ are
not expected from conventional stellar evolution, but can be produced naturally
via neutron star (NS) implosions induced by capture of small primordial black
holes (PBHs) or from accumulation of some varieties of particle dark matter. We
argue that a unique signature of such "transmuted" solar-mass BHs is that their
mass distribution would follow that of the NSs. This would be distinct from the
mass function of black holes in the solar-mass range predicted either by
conventional stellar evolution or early Universe PBH production. We propose
that analysis of the solar-mass BH population mass distribution in a narrow
mass window of $\sim 1-2.5\,{\rm M}_\odot$ can provide a simple yet powerful
test of the origin of these BHs. Recent LIGO/VIRGO gravitational wave (GW)
observations of the binary merger events GW190425 and GW190814 are consistent
with a BH mass in the range $\sim 1.5-2.6~M_{\odot}$. Though these results have
fueled speculation on dark matter-transmuted solar-mass BHs, we demonstrate
that it is unlikely that the origin of these particular events stems from NS
implosions. Data from upcoming GW observations will be able to distinguish
between solar-mass BHs and NSs with high confidence. This capability will
facilitate and enhance the efficacy of our proposed test.
