A blast from the infant Universe: The very high-<i>z</i>GRB 210905A

We present a detailed follow-up of the very energetic GRB 210905A at high redshift z = 6.312 and its luminous X-ray optical afterglow. Following detection by Swift Konus- Wind , we obtained photometric spectroscopic in near-infrared (NIR), covering both prompt afterglow emission from few minutes up to 20 Ms after burst. With an isotropic gamma-ray energy release E iso 1.27 −0.19 +0.20 × 10 54 erg, lies top ∼7% bursts (GRBs) catalogue terms released. Its is among most ever observed, and, particular, it one t ≳ 0.5 d rest frame. The starts with shallow evolution that can be explained injection, followed steeper decay, while spectral distribution agreement slow cooling constant-density environment within standard fireball theory. A jet break ∼46.2 ± 16.3 (6.3 2.2 rest-frame) has been observed light curve; however, hidden H band due constant contribution host galaxy potentially foreground intervening galaxy. In only fourth &gt; 6 known date. By assuming number density n 1 cm −3 efficiency η 0.2, derived half-opening angle 8.4 ° ±1.0°, which highest measured for burst, but range covered closer events. resulting collimation-corrected ≃1 52 erg also measured. moderately large argues against recent claims inverse dependence on redshift. total likely too sustained magnetar, suggests central engine this burst was newly formed black hole. Despite outstanding energetics luminosity afterglow, demonstrate they are consistent 2 σ those less distant bursts, indicating powering mechanisms progenitors do not evolve significantly