Impact of a mean field dynamo on neutron star mergers leading to magnetar remnants
Impact of a mean field dynamo on neutron star mergers leading to magnetar remnants
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DOI：
10.1103/physrevd.108.123012
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发表时间：
2023-11
影响因子：
5
通讯作者：
E. Most
中科院分区：
文献类型：
--
作者：
E. Most
我们研究了平均场模型对在双中子星合并后阶段可能活跃的$\alpha\Omega$ -发电机的影响。为此，我们推导了理想广义相对论磁流体动力学（GRMHD）的方程，其中包含一个额外的$\alpha-$项，它与牛顿的对应项非常相似，但与标准的数值相对论模拟保持兼容。对于差转磁星残骸及其吸积盘外层磁旋转不稳定性驱动的湍流发电机，我们提出了一个启发式发电机闭合关系。作为第一个演示，我们将此框架应用于合并后演变的早期阶段（$\lesssim 50\, \rm ms$）。我们证明，根据发电机作用的有效性，磁驱动的外流可以存在，其重子负载的数量与磁场放大相关。在进入准稳定状态之前，这些流出物也可能包含前体燃烧事件。对于本工作中探索的发电机参数，我们观察到电磁能量通量高达$10^{50}\, \rm erg/s$，尽管更大的放大参数可能会导致更强的通量。我们的结果与预期一致，即大量的发电机放大（在合并期间或之后）可能是中子星残余物为短伽马射线爆发或其前兆提供能量所必需的。
We investigate the impact of a mean field model for the $\alpha\Omega$-dynamo potentially active in the post-merger phase of a binary neutron star coalescence. We do so by deriving equations for ideal general relativistic magnetohydrodynamics (GRMHD) with an additional $\alpha-$term, which closely resemble their Newtonian counterpart, but remain compatible with standard numerical relativity simulations. We propose a heuristic dynamo closure relation for the magnetorotational instability-driven turbulent dynamo in the outer layers of a differentially rotating magnetar remnant and its accretion disk. As a first demonstration, we apply this framework to the early stages of post-merger evolution ($\lesssim 50\, \rm ms$). We demonstrate that depending on the efficacy of the dynamo action, magnetically driven outflows can be present with their amount of baryon loading correlating with the magnetic field amplification. These outflows can also contain precursor flaring episodes before settling into a quasi-steady state. For the dynamo parameters explored in this work, we observe electromagnetic energy fluxes of up to $10^{50}\, \rm erg/s$, although larger amplification parameters will likely lead to stronger fluxes. Our results are consistent with the expectation that substantial dynamo amplification (either during or after the merger) may be necessary for neutron-star remnants to power short gamma-ray bursts or precursors thereof.