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arXiv 1604.02679astro-ph.SRastro-ph.GA
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行星状星云IC $\,$ 418中首次发现$^3$ He $^+$

First Detection of $^3$He$^+$ in the Planetary Nebula IC$\,$418

L. Guzman-Ramirez, J. R. Rizzo, A. A. Zijlstra, C. García-Miró, C. Morisset, M. D. Gray

摘要:

$^3$ He同位素对天体物理学的许多领域都很重要,包括恒星演化、化学演化和宇宙学。这种同位素是在低质量恒星中产生的,它们通过行星状星云(PN)阶段演化。$^3$氦在PNe中的丰度可以帮助测试银河系化学演化的模型。我们提出了探测的$^3$他$^+$发射线使用单碟深空站63,对PN IC $\,$ 418。我们推导出的$^3$ He/H丰度范围为1.74 $\pm$ 0.8 $\times$ 10 $^{-3}$至5.8 $\pm$ 1.7 $\times$ 10 $^{-3}$,取决于该线的一部分是否出现在外部电离晕中。较低的值为$^3$ He/H比接近恒星模型预测的值,其中包括热盐混合,但需要大量的$^3$ He产生的低质量恒星,丰富的星际介质(ISM)。然而,这高估了HII区域、ISM和原太阳颗粒中的$^3$ He丰度,已知其为10 $^{-5}$的量级。这种差异质疑了我们对$^3$ He从星周环境到ISM的演化的理解。

英文摘要:

The $^3$He isotope is important to many fields of astrophysics, including stellar evolution, chemical evolution, and cosmology. The isotope is produced in low-mass stars which evolve through the planetary nebula (PN) phase. $^3$He abundances in PNe can help test models of the chemical evolution of the Galaxy. We present the detection of the $^3$He$^+$ emission line using the single dish Deep Space Station 63, towards the PN IC$\,$418. We derived a $^3$He/H abundance in the range 1.74$\pm$0.8$\times$10$^{-3}$ to 5.8$\pm$1.7$\times$10$^{-3}$, depending on whether part of the line arises in an outer ionized halo. The lower value for $^3$He/H ratio approaches values predicted by stellar models which include thermohaline mixing, but requires that large amounts of $^3$He are produced inside low-mass stars which enrich the interstellar medium (ISM). However, this over-predicts the $^3$He abundance in HII regions, the ISM, and proto-solar grains, which is known to be of the order of 10$^{-5}$. This discrepancy questions our understanding of the evolution of the $^3$He, from circumstellar environments to the ISM.

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