The nature of the gamma-ray burst (GRB) central engine still remains an enigma. Entities widely believed to be capable of powering the extreme jets are magnetars and black holes. The maximum rotational energy that is available in a millisecond magnetar to form a jet is ∼10⁵² erg. We identify eight long GRBs whose jet-opening angle-corrected energetics of the prompt emission episode are >10⁵² erg with high confidence level and, therefore, their central engines are expected to be black holes. The majority of these GRBs present significant emission in the sub-GeV energy range. The X-ray afterglow light curves of these bursts do not show any shallow decay behavior such as a plateau; however, a few cases exhibit flares and multiple breaks instead of a single power-law decay. For a minimum mass of the black hole (∼2 M _⊙), we find the efficiency of producing a jet from its rotational energy to range between 2% and 270%. Highly energetic jets requiring high efficiencies implies that either the mass of these black holes are much larger or there are, in addition, other sources of energy that power the jet. By considering the Blandford–Znajek mechanism of jet formation, we estimate the masses of these black holes to range between ∼2 and 60 M _⊙. Some of the lighter black holes formed in these catastrophic events are likely candidates to lie in the mass-gap region (2–5 M _⊙).

伽马射线暴（GRB）中央引擎的性质仍然是一个谜。人们普遍认为能够为极端喷气机提供动力的实体是磁星和黑洞。毫秒级磁星中可用于形成射流的最大旋转能量约为10 ⁵² erg。我们确定了8个长GRB，其快速发射事件的射流张开角校正的能量大于10 ⁵²erg具有很高的置信度，因此，其中央引擎可能会出现黑洞。这些GRB中的大多数在次GeV能量范围内呈现出显着的发射。这些脉冲的X射线余辉光曲线没有表现出任何浅的衰减行为，例如平稳。但是，少数情况下会出现耀斑和多次中断，而不是单个幂律衰减。对于黑洞（〜2的最小质量中号 _⊙），我们发现从旋转能量产生射流的效率在2％至270％之间。需要高效率的高能射流意味着这些黑洞的质量要大得多，或者还有为射流提供动力的其他能源。通过考虑喷射形成布兰福德-Znajek机制，我们估计这些黑洞群众范围〜2和60之间中号 _⊙。一些形成在这些灾难性事件的打火机黑洞是可能的候选者躺在质间隙区域（2-5中号 _⊙）。