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arXiv 2402.18299astro-ph.HE
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IIP型超新星早期光谱中宽He II 4686Å发射的起源

Origin of broad He II 4686Å emission in early spectra of type IIP supernovae

Nikolai Chugai, Victor Utrobin

AI总结:

针对SN 2020jfo早期光谱中的宽He II 4686Å发射,研究提出正向激波热气体中致密碎片模型,并通过氦氢电离激发计算解释其光度、线强比和光学厚度。

摘要:

我们提出了一个模型,用于解释II型超新星SN 2020jfo早期光谱中宽He II 4686Å发射的起源。4686Å谱线推测由嵌在正向激波炽热气体中的致密碎片发射。这些碎片产生于抛射物边界处致密低质量壳层的剧烈制动以及同时发生的Rayleigh-Taylor不稳定性。发射谱线碎片的温度约为5×10^4 K。对氦和氢的电离与激发计算解释了He II 4686Å光度、较大的He II 4686Å/Hα通量比,以及4686Å谱线显著的光学厚度。我们证明,正向激波后炽热电子对碎片的加热补偿了通过He II 304Å发射造成的冷却。

英文摘要:

We propose a model for the origin of the broad He II 4686A emission in the early spectrum of type II SN~2020jfo. The 4686A line is emitted presumably by dense fragments embedded into a hot gas of the forward shock wave. The fragments are produced as a result of a heavy braking of the dense low-mass shell at the ejecta boundary and a simultaneous Rayleigh-Taylor instability. The temperature of line-emitting fragments is $\approx$5$\times10^4$K. Calculations of ionization and excitation of helium and hydrogen account for the He II 4686A luminosity, the large flux ratio of He II 4686A/H$α$, and a significant optical depth of the 4686A line. We demonstrate that fragments heating by hot electrons behind the forward shock compensates cooling via the HeII 304A emission.

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