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arXiv 1804.08652astro-ph.HE
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具有X射线余辉平台的伽玛暴的磁星起源

On the magnetar origin of the GRBs presenting X-ray afterglow plateaus

G. Stratta, M. G. Dainotti, S. Dall'Osso, X. Hernandez, G. De Cesare

摘要:

在许多伽马射线暴(GRB)中观测到的X射线余辉平台发射被解释为是由落回新形成的黑洞或由超磁化毫秒中子星的自旋下降光度提供燃料的。如果采用后一种模型,伽玛暴X射线余辉光变曲线可以解析地再现。我们拟合了一个GRB X射线平台的样本,有趣的是,得到了与$B\propto P^{7/6}$一致的磁场-自旋周期(B-P)图中的分布。这是预期从完善的物理学的自旋线最小周期的银河系毫秒彗星。我们得到的关系的归一化完全匹配自旋线预测的预期质量($\sim 1 M_{\odot}$)和半径($\sim 10 {\rm ~km}$)的新诞生的磁星,和质量吸积率符合伽玛射线暴的预期$10^{-4} M_{\odot}/{\rm s} <\dot{M}< 10^{-1} M_{\odot}/{\rm s}$。扩展发射的短伽玛暴(SEE)出现在高周期的末端,而长伽玛暴(LGRB)出现在短周期的末端。这一结果与自旋上极限的预期是一致的,其中总的吸积质量决定了中子星在B-P图中的位置。LGRB和SEE的P-B分布在统计上是不同的,进一步支持基本平面关系\citep{dainotti16c,Dainotti2017}在这些群体之间是一个强大的判别式的想法。我们的结论是强大的对假设的伽玛射线暴准直角和磁星破碎指数,这将产生的磁星属性平行的自旋线,并强烈支持磁星起源的伽玛射线暴呈现X射线高原。

英文摘要:

The X-ray afterglow plateau emission observed in many Gamma-ray Bursts (GRBs) has been interpreted as either being fueled by fallback onto a newly formed black hole, or by the spin-down luminosity of an ultra-magnetized millisecond neutron star. If the latter model is assumed, GRB X-ray afterglow light curves can be analytically reproduced. We fit a sample of GRB X-ray plateaus, interestingly yielding a distribution in the magnetic field versus spin period (B-P) diagram consistent with $B\propto P^{7/6}$. This is expected from the well-established physics of the spin-up line minimum period for Galactic millisecond pulsars. The normalisation of the relation we obtain perfectly matches spin-up line predictions for the expected masses ($\sim 1 M_{\odot}$) and radii ($\sim 10 {\rm ~km}$) of newly born magnetars, and mass accretion rates consistent with GRB expectations of $10^{-4} M_{\odot}/{\rm s} <\dot{M}< 10^{-1} M_{\odot}/{\rm s}$. Short GRBs with extended emission (SEE) appear towards the high period end of the distribution, while the long GRBs (LGRBs) towards the short period end. This result is consistent with spin-up limit expectations where the total accreted mass determines the position of the neutron star in the B-P diagram. The P-B distribution for LGRBs and SEE are statistically different, further supporting the idea that the fundamental plane relation \citep{dainotti16c,Dainotti2017} is a powerful discriminant among those populations. Our conclusions are robust against suppositions regarding the GRB collimation angle and magnetar breaking index, which shifts the resulting magnetar properties parallel to the spin-up line, and strongly support a magnetar origin for GRBs presenting X-ray plateaus.

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