Some First Stars Were Red: Detecting Signatures of Massive Population
  III Formation Through Long-Term Stochastic Color Variations
  Identifying stars formed in pristine environments (Pop III) within the first
billion years is vital to uncovering the earliest growth and chemical evolution
of galaxies. Pop III galaxies, however, are typically expected to be too faint
and too few in number to be detectable by forthcoming instruments without
extremely long integration times and/or extreme lensing. In an environment,
however, where star formation is suppressed until a halo crosses the atomic
cooling limit (e.g., by a modest Lyman-Werner flux, high baryonic streaming
velocities, and/or dynamical heating effects),primordial halos can form
substantially more numerous and more massive stars. Some of these stars will
in-turn be accreting more rapidly than they can thermally relax at any given
time. Using high resolution cosmological zoom-in simulations of massive star
formation in high-z halos, we find that such rapidly accreting stars produce
prominent spectral features which would be detectable by {\it JWST}. The rapid
accretion episodes within the halo lead to stochastic reprocessing of 0--20\%
of the total stellar emission into the rest-frame optical over long timescales,
a unique signature which may allow deep observations to identify such objects
out to $z \sim 10-13$ using mid- and wide-band NIRCam colors alone.
