Finding the First Cosmic Explosions. IV. 90 - 140 M$_{\odot}$
  Pair-Instability Supernovae
  Population III stars that die as pair-instability supernovae are usually
thought to fall in the mass range of 140 - 260 M$_{\odot}$. But several lines
of work have now shown that rotation can build up the He cores needed to
encounter the pair instability at stellar masses as low as 90 $_{\odot}$.
Depending on the slope of the initial mass function of Population III stars,
there could be 4 - 5 times as many stars from 90 - 140 $_{\odot}$ in the
primordial universe than in the usually accepted range. We present numerical
simulations of the pair-instability explosions of such stars performed with the
MESA, FLASH and RAGE codes. We find that they will be visible to supernova
factories such as Pan-STARRS and LSST in the optical out to z $\sim$ 1 - 2 and
to JWST and the 30 m-class telescopes in the NIR out to $z \sim$ 7 - 10. Such
explosions will thus probe the stellar populations of the first galaxies and
cosmic star formation rates in the era of cosmological reionization. These
supernovae are also easily distinguished from more massive pair-instability
explosions, underscoring the fact that there is far greater variety to the
light curves of these events than previously understood.
