The Origin of Fluorine: Abundances in AGB Carbon Stars Revisited
The Origin of Fluorine: Abundances in AGB Carbon Stars Revisited
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氟的起源：重新审视 AGB 碳星中的丰度
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
P. Laverny
中科院分区：
文献类型：
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作者：
C. Abia;K. Cunha;S. Cristallo;P. Laverny
修订后的光谱参数的HF分子和一个新的CN线列表中的2.3亩地区最近已提供，允许修订的F含量在AGB星。AGB碳星是唯一经观测证实的氟源。目前，关于AGB星在银河系化学演化中的相关性还没有达成共识。这篇文章的目的是更好地限制这些恒星的贡献，更准确地估计它们的氟丰度。使用新的光谱工具和LTE光谱合成，我们重新确定氟丰度从几个HF线在K波段的银河系和河外AGB碳恒星的光谱类型N，J和SC跨越广泛的金属丰度的样本。平均而言，新衍生的氟丰度系统地降低了0.33德克斯相对于以前的测定。这可能来自HF线的较低激发能量和这里使用的较大宏观湍流参数的组合，以及来自新采用的CN线列表。然而，AGB星的理论核合成模型与太阳金属丰度的新氟测定一致。在低金属丰度，理论和观测之间的协议，可以通过以不同的方式处理的辐射/对流界面的对流信封的基础上找到。新的氟光谱测量同意在低和太阳金属丰度的理论模型。尽管如此，需要补充来源来解释在太阳附近观测到的丰度。
Revised spectroscopic parameters for the HF molecule and a new CN line list in the 2.3 mu region have been recently available, allowing a revision of the F content in AGB stars. AGB carbon stars are the only observationally confirmed sources of fluorine. Nowadays there is not a consensus on the relevance of AGB stars in its Galactic chemical evolution. The aim of this article is to better constrain the contribution of these stars with a more accurate estimate of their fluorine abundances. Using new spectroscopic tools and LTE spectral synthesis, we redetermine fluorine abundances from several HF lines in the K-band in a sample of Galactic and extragalactic AGB carbon stars of spectral types N, J and SC spanning a wide range of metallicities. On average, the new derived fluorine abundances are systematically lower by 0.33 dex with respect to previous determinations. This may derive from a combination of the lower excitation energies of the HF lines and the larger macroturbulence parameters used here as well as from the new adopted CN line list. Yet, theoretical nucleosynthesis models in AGB stars agree with the new fluorine determinations at solar metallicities. At low metallicities, an agreement between theory and observations can be found by handling in a different way the radiative/convective interface at the base of the convective envelope. New fluorine spectroscopic measurements agree with theoretical models at low and at solar metallicity. Despite this, complementary sources are needed to explain its observed abundance in the solar neighbourhood.