Central engine of the highest redshift blazar

We present the results of a new LUCI/Large Binocular Telescope near-infrared (NIR) spectroscopic observation PSO J030947.49+271757.31 (hereafter J0309+27), highest redshift blazar known to date ( z ∼ 6.1). From CIV λ 1549 broad emission line, we found that J0309+27 is powered by 1.45 −0.85 +1.89 × 10 9 M ⊙ supermassive black hole (SMBH) with bolometric luminosity ∼8 46 erg s −1 and an Eddington ratio equal 0.44 −0.35 +0.78 . also obtained photometric observations Telescopio Nazionale Galileo in J K bands better constrain NIR spectral energy distribution source. Thanks these observations, were able model accretion disk derive independent estimate mass J0309+27, confirming value inferred from virial technique. The existence such massive SMBH just ∼900 million years after Big Bang challenges models earliest growth, especially if jetted active galactic nuclei are indeed associated highly spinning hole, as currently assumed. In Eddington-limited scenario assuming radiative efficiency 0.3, typical fast rotating SMBH, seed more than 6 at = 30 required reproduce 6. This requirement suggests either earlier periods rapid growth super-Eddington or which only part released gravitational goes toward heating feeding hole.