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arXiv 2304.14331astro-ph.HE
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浅角结构喷流产生的 GRB 221009A 余辉

GRB 221009A Afterglow from a Shallow Angular Structured Jet

Ramandeep Gill, Jonathan Granot

AI总结:

本文利用考虑正反向激波的动力学模型分析 GRB 221009A 多波段余辉,发现其喷流具有窄核和浅角结构,并膨胀进入恒星风中,同时表明仅少部分激波加热电子形成幂律能量分布。

摘要:

异常明亮的伽马射线暴(GRB)余辉能够揭示其喷流的角结构。GRB 喷流似乎具有一个窄核(半张角为 $θ_c$),超出该范围后,其动能随偏离喷流对称轴的角度 $θ$ 呈幂律下降,弱磁化喷流会经历显著的混合,导致浅($a\lesssim2$)角分布。我们利用 GRB 221009A 精确的多波段余辉观测,通过一个同时考虑正向激波和反向激波的动力学模型,来约束喷流的角结构,其中外部密度呈幂律分布 $n_{\rm{}ext}\propto{}R^{-k}$。主导光学和 X 射线通量的正向激波辐射,以及产生射电余辉的反向激波辐射,均要求喷流具有窄核($θ_c\approx0.021$)和浅角结构($a\approx0.8$),且膨胀进入恒星风($k\approx2$)中。此外,这些数据似乎倾向于在两种激波中,仅有小部分($ξ_e\approx10^{-2}$)激波加热电子形成了幂律能量分布。

英文摘要:

Exceptionally bright gamma-ray burst (GRB) afterglows can reveal the angular structure of their jets. GRB jets appear to have a narrow core (of half-opening angle $θ_c$), beyond which their kinetic energy drops as a power-law with angle $θ$ from the jet's symmetry axis, $E_{k,\rm iso}(θ)\propto[1+(θ/θ_c)^2]^{-a/2}$. The power-law index $a$ reflects the amount of mixing between the shocked jet and confining medium, which depends on the jet's initial magnetization. Weakly magnetized jets undergo significant mixing, leading to shallow ($a\lesssim2$) angular profiles. We use the exquisite multi-waveband afterglow observations of GRB 221009A to constrain the jet angular structure using a dynamical model that accounts for both the forward and reverse shocks, for a power-law external density profile, $n_{\rm{}ext}\propto{}R^{-k}$. Both the forward-shock emission, that dominates the optical and X-ray flux, and the reverse-shock emission, that produces the radio afterglow, require a jet with a narrow core ($θ_c\approx0.021$) and a shallow angular structure ($a\approx0.8$) expanding into a stellar wind ($k\approx2$). Moreover, these data appear to favor a small fraction ($ξ_e\approx10^{-2}$) of shock-heated electrons forming a power-law energy distribution in both shocks.

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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