Pair-instability and super-luminous supernova discoveries at z = 2.05, z = 2.50, and z = 3.90

We present the discovery of three super-luminous supernovae (SLSNe) at z = 2 - 4 as part of our survey to detect ultraviolet-luminous supernova at z > 2. SLSNe are ≥10 times more luminous than normal supernova types, reaching peak luminosities of ≳10^(44) erg s^(−1). A small subset of SLSNe (type SLSN-R) exhibit a slow evolution, and thus enormous integrated energies (≳10^(51) erg), consistent with the radiative decay of several solar masses of 56 Ni. SLSN-R are believed to be the deaths of very massive stars, ∼140 - 260 M_⊙, that are theorized to result in pair-instability supernovae. Two of the high redshift SLSNe presented here are consistent with the behavior of SLSN-R out to the extent in which their light curves are sampled, with the third event being consistent with the more rapid fade of the type II-L SLSN SN 2008es at z = 0.205. SLSNe are extremely rare locally but are expected to have been more common in the early Universe and as members of the first generation of stars to form after the Big Bang, the Population III stars. The high intrinsic luminosity of SLSNe and their detectability using our image-stacking technique out to z ∼ 6 provide the first viable route to detect and study the deaths of massive Population III stars which are expected to form in pristine gas at redshifts as low as z ∼ 2