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arXiv 2606.25035astro-ph.HE
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快速射电暴模型中的动能瓶颈

The kinetic-energy bottleneck in Fast Radio Burst models

The Open University of Israel(以色列开放大学);Astrophysics Research Center of the Open university (ARCO)(以色列开放大学天体物理研究中心);The George Washington University(乔治华盛顿大学);University of Texas at Austin(德克萨斯大学奥斯汀分校)

Paz Beniamini, Pawan Kumar

AI总结:

本文推导了FRB发射机制的模型无关约束,推断发射区的密度、尺寸和洛伦兹因子,评估三类模型:内磁层模型、光柱尺度重连模型和外激波脉泽模型,发现持续粒子加速是必要的,且外激波脉泽模型面临诱导康普顿散射光学厚问题。

摘要:

大多数快速射电暴(FRB)模型涉及一个两步过程:中心引擎释放的能量转化为粒子动能,随后才辐射为相干的GHz发射。我们推导了FRB发射机制的模型无关约束,并利用它们推断发射区的密度、尺寸和粒子洛伦兹因子。我们评估了对三类主要FRB模型的影响。(i)内磁层模型违反亮温度与动能光度约束,除非粒子在本地持续再加速。磁星强度的磁场可以在$R\lesssim10^{10} \mathrm{cm}$范围内提供所需的平行电场,并带有额外的模型依赖约束。怪物激波情景提供了这种持续加速,但要求粒子密度超过Goldreich-Julian值$\gtrsim 10^{12}$,对于典型FRB光度,这将脉泽峰值移至$\gtrsim10^3$ GHz。(ii)光柱尺度上的受迫重联提供持续粒子加速,但从压缩重联层发射的射电能量通常仅为注入能量的$\lesssim10^{-6}$。(iii)外激波脉泽模型满足动能光度和亮温度约束。然而,我们表明上游风不可避免地对诱导康普顿散射光学厚,独立于模型的主要参数。提出的逃逸路径——在脉泽峰值之上发射或上游磁化参数$\sigma_{\rm w}\gtrsim30$——导致极低的效率,而前者也与窄FRB谱冲突。我们得出结论,在中子星表面附近运行并包含持续粒子加速的磁层模型仍然是最有前景的FRB发射情景,但需成功从磁层逃逸(在引言中讨论)。

英文摘要:

Most Fast Radio Burst (FRB) models invoke a two-step process in which energy released by the central engine is converted into particle kinetic energy and only subsequently radiated as coherent GHz emission. We derive model-independent constraints on FRB emission mechanisms and use them to infer the density, size, and particle Lorentz factor of the emitting region. We assess the implications for the three main classes of FRB models. (i) Inner-magnetospheric models violate brightness-temperature and kinetic-luminosity constraints unless particles are continuously re-accelerated in situ. Magnetar-strength magnetic fields can supply the required parallel electric field out to $R\lesssim10^{10} \mathrm{cm}$ with additional, model-dependent constraints. The monster-shock scenario provides such continuous acceleration, but requires particle densities exceeding the Goldreich-Julian value by $\gtrsim 10^{12}$, shifting the maser peak to $\gtrsim10^3$ GHz for typical FRB luminosities. (ii) Light-cylinder-scale forced-reconnection provides continuous particle acceleration but the radio energy emitted from the compressed reconnection layer is typically only $\lesssim10^{-6}$ of the injected energy. (iii) External-shock maser models satisfy kinetic-luminosity and brightness-temperature constraints. However, we show that the upstream wind is unavoidably optically thick to induced Compton scattering, independent of the model's principal parameters. Proposed escape routes - emission above the maser peak or upstream magnetization $σ_{\rm w}\gtrsim30$ - lead to tiny efficiencies, while the former also conflicts with narrow FRB spectra. We conclude that magnetospheric models operating near the neutron-star surface and incorporating continuous particle acceleration remain the most promising FRB emission scenario, subject to successful wave escape from the magnetosphere (discussed in the Introduction).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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