One of the most elusive features of Gamma Ray Bursts (GRBs) is the sporadicemission prior to the main prompt event observed in at least $\sim 15\%$ ofcases. These precursors have spectral and temporal properties similar to themain prompt emission, and smaller, but comparable, energetics. They areseparated from the main event by a quiescent time that may be extremely longand, in some cases, more than one precursor has been observed in the sameburst. Precursors are still a puzzle: despite many attempts none of theproposed models can account for all the observed features. Based on thecomplete sample of bright long GRBs observed by Swift (BAT6), we propose a newscenario for which precursors are explained by assuming that the central GRBengine is a newly born magnetar. In this model the precursor and the promptemission arise from accretion of matter onto the surface of the magnetar. Theaccretion process can be halted by the centrifugal drag exerted by the rotatingmagnetosphere onto the in-falling matter, allowing for multiple precursors andvery long quiescent times.
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机译：Gamma Ray Bursts（GRB）最难以捉摸的特征之一是，在至少$ \ sim 15 \％$的情况下，在发生主要提示事件之前发生了零星遗漏。这些前体具有类似于主要瞬态发射的光谱和时间特性，并且具有较小但可比的高能。它们与主要事件之间的间隔时间可能非常长，并且在某些情况下，在同一爆发中观察到多个前体。前体仍然是一个难题：尽管进行了许多尝试，但所提出的模型都无法解释所有观察到的特征。基于Swift（BAT6）观测到的明亮的长GRB的完整样本，我们提出了一个新闻场景，假设中央GRB引擎是新生的磁星，对此前兆进行了解释。在该模型中，前驱物和瞬态发射是由于物质在电磁体表面上的积聚而产生的。旋转磁层施加在下落的物质上的离心阻力可以阻止吸积过程，从而允许多种前体和非常长的静止时间。
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