Strong gravitational lensing by galaxy clusters has become a powerful tool for probing the high-redshift Universe , magnifying distant and faint background galaxies .
Reliable strong lensing ( SL ) models are crucial for determining the intrinsic properties of distant , magnified sources and for constructing their luminosity function .
We present here the first SL analysis of MACS J0308.9+2645 and PLCK G171.9-40.7 , two massive galaxy clusters imaged with the Hubble Space Telescope in the framework of the Reionization Lensing Cluster Survey ( RELICS ) .
We use the Light-Traces-Mass modeling technique to uncover sets of multiply imaged galaxies and constrain the mass distribution of the clusters .
Our SL analysis reveals that both clusters have particularly large Einstein radii ( \theta _ { E } > 30 \arcsec for a source redshift of z _ { s } = 2 ) , providing fairly large areas with high magnifications , useful for high-redshift galaxy searches ( \sim 2 arcmin ^ { 2 } with \mu > 5 to \sim 1 arcmin ^ { 2 } with \mu > 10 , similar to a typical Hubble Frontier Fields cluster ) .
We also find that MACS J0308.9+2645 hosts a promising , apparently bright ( J \sim 23.2 - 24.6 AB ) , multiply imaged high-redshift candidate at z \sim 6.4 .
These images are amongst the brightest high-redshift candidates found in RELICS .
Our mass models , including magnification maps , are made publicly available for the community through the Mikulski Archive for Space Telescopes .