Possible evidence of QCD axion stars in HSC and OGLE microlensing events
  Dark matter in the form of axions is expected to form miniclusters, and their
dense regions can harbor compact axion stars. Such axion stars could be
discovered by microlensing events. In particular, some candidate events
reported by Subaru HSC and OGLE can be explained simultaneousely if the axion
stars with masses of the order of the Earth mass make up about $\sim$20% of
dark matter. For QCD axions, this corresponds to the axion mass in the range
$10^{-9}-10^{-6}$ eV, which is consistent with the experimental constraints, as
well as the cosmological anthropic window of parameters.
