  Presently, primordial black holes (PBHs) in the asteroid-mass window from
$10^{-16}$ M$_\odot$ to $10^{-10}$ M$_\odot$ are a popular dark matter
candidate. If they exist, some stars would capture them upon formation, and
they would slowly accrete the star over gigayears. Such Hawking stars -- stars
with a central PBH -- provide a novel channel for the formation of both
sub-Chandrasekhar mass black holes as well as red straggler stars. Here we
report on stellar evolution models that extend our previous work to Hawking
stars with masses between 0.5 and 1.4 M$_\odot$. We explore three accretion
schemes, and find that a wide range of PBHs in the asteroid-mass window can
robustly accrete stars as small as 1 M$_{\odot}$ within the age of the
Universe. This mechanism of producing sub-solar mass black holes is highly
dependent on the assumed accretion physics and stellar metallicity.
Lower-metallicity stars are generally accreted more rapidly, suggesting that it
may be more likely for sub-Chandrasekhar mass Hawking stars formed in the early
universe, such as those in ultra-faint dwarf (UFD) galaxies, to transmute their
star into a sub-Chandrasekhar mass black hole within a Hubble time. We present
a stellar population synthesis of a Draco II-like UFD galaxy containing Hawking
stars and show that the number of red stragglers they produce can qualitatively
match the observed population.
