Discovery of a hyperluminous quasar at z = 1.62 with Eddington ratio > 3 in the eFEDS field confirmed by KOOLS-IFU on Seimei Telescope

We report the discovery of a hyperluminous type 1 quasar (eFEDS J082826.9-013911; eFEDSJ0828-0139) at zspec = 1.622 with a super-Eddington ratio (λEdd). We perform the optical spectroscopic observations with KOOLS-IFU on the Seimei Telescope. The black hole mass (MBH) based on the single-epoch method with MgII λ2798 is estimated to be MBH = (6.2 ± 1.2) × 10⁸ M_. To measure the precise infrared luminosity (LIR), we obtain submillimeter data taken by SCUBA-2 on JCMT and conduct the spectral energy distribution analysis with X-ray to submillimeter data. We find that LIR of eFEDSJ0828-0139 is LIR = (6.8 ± 1.8) × 10¹³ L_, confirming the existence of a hypeluminous infrared galaxy (HyLIRG). λEdd is estimated to be λEdd = 3.6 ± 0.7, making it one of the quasars with the highest BH mass accretion rate at cosmic noon.