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We present the discovery of the very energetic GRB 210905A at the high redshift z=6.312 and its luminous X-ray and optical afterglow. With an isotropic gamma-ray energy of Eiso$\sim 10^{54}$ erg, GRB 210905A lies in the top 7% GRBs in the Konus-Wind Catalog in terms of energy released. Its afterglow is also among the most luminous ever observed, and, in particular in the optical at $>$0.5 d (rest frame). The early afterglow light curve can be explained by energy injection and the spectral energy distribution is in agreement with slow cooling in a constant-density environment. The half-opening angle is within the range covered by closer events and thus argues against recent claims of an inverse dependence of the half-opening angle on the redshift. The collimation-corrected released gamma-ray energy of'1×1052erg which is also among the highest ever measured.
Despite the great released energy, our findings demonstrate that the properties of this burst are in agreement with those of less distant burst. ADS link: https://ui.adsabs.harvard.edu/abs/2022arXiv220204544R/abstract
