RELICS: A Strong Lens Model for SPT-CLJ0615-5746, a z=0.972 Cluster
  We present a lens model for the cluster SPT-CLJ0615$-$5746, which is the
highest redshift ($z=0.972$) system in the Reionization of Lensing Clusters
Survey (RELICS), making it the highest redshift cluster for which a full strong
lens model is published. We identify three systems of multiply-imaged lensed
galaxies, two of which we spectroscopically confirm at $z=1.358$ and $z=4.013$,
which we use as constraints for the model. We find a foreground structure at
$z\sim0.4$, which we include as a second cluster-sized halo in one of our
models; however two different statistical tests find the best-fit model
consists of one cluster-sized halo combined with three individually optimized
galaxy-sized halos, as well as contributions from the cluster galaxies
themselves. We find the total projected mass density within $r=26.7"$ (the
region where the strong lensing constraints exist) to be
$M=2.51^{+0.15}_{-0.09}\times 10^{14}$~M$_{\odot}$. If we extrapolate out to
$r_{500}$, our projected mass density is consistent with the mass inferred from
weak lensing and from the Sunyaev-Zel'dovich effect
($M\sim10^{15}$~M$_{\odot}$). This cluster is lensing a previously reported
$z\sim10$ galaxy, which, if spectroscopically confirmed, will be the
highest-redshift strongly lensed galaxy known.
