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arXiv 1401.1972astro-ph.HE
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一颗磁星为普通怪物GRB 130427 A提供动力?

A magnetar powering the ordinary monster GRB 130427A?

M. G. Bernardini, S. Campana, G. Ghisellini, P. D'Avanzo, G. Calderone, S. Covino, G. Cusumano, G. Ghirlanda, V. La Parola, A. Maselli, A. Melandri R. Salvaterr… 展开作者

M. G. Bernardini, S. Campana, G. Ghisellini, P. D'Avanzo, G. Calderone, S. Covino, G. Cusumano, G. Ghirlanda, V. La Parola, A. Maselli, A. Melandri R. Salvaterra, D. Burlon, V. D'Elia, D. Fugazza, B. Sbarufatti, S. D. Vergani, G. Tagliaferri

摘要:

在假设伽玛暴的中心引擎是一颗吸积驱动的磁星的前提下,对异常明亮的伽马射线暴(GRB)130427 A进行了分析。在这个框架中,最初提出的解释伽玛暴的前体活动,即时发射产生的物质吸积到一个新诞生的磁星,所观察到的功率与吸积率。如果离心力能够暂停吸积,那么发射最终会停止。我们表明,X射线和光学余辉很好地解释为前向冲击发射与射流中断加上贡献的磁星的自旋下降。我们的模型不需要任何贡献的反向冲击,这可能仍然会影响余辉光曲线在无线电和毫米频率,或在早期的光学。我们导出了磁星的磁场($B\sim 10^{16}$ G)和自旋周期($P\sim 20$ ms),并得到了吸积最小光度的独立估计。这一最小光度结果远低于GRB 130427 A的瞬发发光光度,为整个瞬发发光是磁星持续吸积的结果的情况提供了强有力的一致性检查。这与磁星相对较长的自旋周期相一致。GRB 130427 A是一个受到良好监测的GRB,显示出非常标准的行为,因此是一个非常合适的基准,以显示吸积动力磁星提供了长GRB特性的独特视角。

英文摘要:

We present the analysis of the extraordinarily bright Gamma-Ray Burst (GRB) 130427A under the hypothesis that the GRB central engine is an accretion-powered magnetar. In this framework, initially proposed to explain GRBs with precursor activity, the prompt emission is produced by accretion of matter onto a newly-born magnetar, and the observed power is related to the accretion rate. The emission is eventually halted if the centrifugal forces are able to pause accretion. We show that the X-ray and optical afterglow is well explained as the forward shock emission with a jet break plus a contribution from the spin-down of the magnetar. Our modelling does not require any contribution from the reverse shock, that may still influence the afterglow light curve at radio and mm frequencies, or in the optical at early times. We derive the magnetic field ($B\sim 10^{16}$ G) and the spin period ($P\sim 20$ ms) of the magnetar and obtain an independent estimate of the minimum luminosity for accretion. This minimum luminosity results well below the prompt emission luminosity of GRB 130427A, providing a strong consistency check for the scenario where the entire prompt emission is the result of continuous accretion onto the magnetar. This is in agreement with the relatively long spin period of the magnetar. GRB 130427A was a well monitored GRB showing a very standard behavior and, thus, is a well-suited benchmark to show that an accretion-powered magnetar gives a unique view of the properties of long GRBs.

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