  Population III stars were the first stars to form after the Big Bang, and are
believed to have made the earliest contribution to the metal content of the
universe beyond the products of the Big Bang Nucleosynthesis. These stars are
theorized to have had extremely short lifespans, and therefore would only be
observable at high redshifts ($z \geq 3-17$) and faint apparent magnitudes
($m_{AB} \gtrsim 40$). The direct detection of Population III stars therefore
remains elusive. However, the recently launched James Webb Space Telescope
(JWST) may be capable of detecting stars in the relevant magnitude range in the
event of favorable gravitational lensing. Theoretical models are required to
interpret these future observations. In this study, new evolutionary models and
non-equilibrium model atmospheres were used to characterize the observable
properties of zero-age main sequence Population III stars. The calculated
models cover a wide range of possible Population III stellar masses, from the
minimum mass predicted by star formation studies to the maximum mass capable of
maintaining hydrostatic equilibrium. Synthetic photometry and theoretical
color-magnitude diagrams were calculated for the bands of the Near-Infrared
Camera (NIRCam) on JWST. The final results are compared to the scales of known
lensing events and JWST magnitude limits. The purpose of this study is to
calculate the observable parameters of Population III stars in the most optimal
JWST bands in order to provide a theoretical foundation for anticipated future
observations of this stellar population.
