The origin of 'cosmic' fluorine is uncertain, but there are three proposed production sites/mechanisms: AGB stars, $ν$ nucleosynthesis in Type II supernovae, and/or the winds of Wolf-Rayet stars. The relative importance of these production sites has not been established even for the solar neighborhood, leading to uncertainties in stellar evolution models of these stars as well as uncertainties in the chemical evolution models of stellar populations.
We determine the fluorine and oxygen abundances in seven bright, nearby giants with well-determined stellar parameters. We use the 2.3 $μ$m vibrational-rotational HF line and explore a pure rotational HF line at 12.2 $μ$m. The latter has never been used before for an abundance analysis. To be able to do this we have calculated a line list for pure rotational HF lines. We find that the abundances derived from the two diagnostics agree.
Our derived abundances are well reproduced by chemical evolution models only including fluorine production in AGB-stars and therefore we draw the conclusion that this might be the main production site of fluorine in the solar neighborhood. Furthermore, we highlight the advantages of using the 12 $μ$m HF lines to determine the possible contribution of the $ν$-process to the fluorine budget at low metallicities where the difference between models including and excluding this process is dramatic.
Fluorine in the Solar Neighborhood: Chemical Evolution Models
根据太阳附近恒星氟丰度的新观测数据，本文提出了检验不同氟核合成处方的化学演化模型，目的是最好地拟合与[F/O] vs. [O/H]和[F/Fe] vs. [Fe/H]丰度比有关的新数据。采用的化学演化模型有：i）经典的“两次落入”模型，它遵循晕厚盘和薄盘相的化学演化，ii）和仅针对薄盘演化设计的“一次落入”模型。我们测试了不同核合成产额来源的预测氟丰度比的影响：AGB星，沃尔夫-拉叶星，II型和Ia型超新星，新星。我们发现氟的产生主要是由AGB星主导的，但需要Wolf-Rayet星才能用我们的化学演化模型再现Jönsson et al.（2017 a）在太阳附近观测数据的趋势。特别地，对于“两次入流”和“一次入流”情况的最佳模型都需要将Meynet和Arnould（2000）给出的Wolf-Rayet产率增加两倍。我们还表明，新星，即使他们的产量仍然是不确定的，可以帮助更好地再现F在[F/O]与[O/H]关系的二级行为。包含沃尔夫-拉叶星的氟生产似乎是复制Jönsson等人在太阳附近观察到的[F/O]与[O/H]的必要条件。此外，新星的列入有助于基本上再现所观察到的氟的二次行为。
Fluorine in the Solar neighborhood: No evidence for the neutrino process
渐近巨星分支恒星是已知的生产“宇宙”氟，但它是不确定的，这些恒星是否是氟在太阳附近的主要生产者，或者如果任何其他建议的形成网站，II型超新星和/或沃尔夫-拉叶星，是更重要的。最近的文章提出了渐近巨星分支恒星以及II型超新星作为太阳附近氟的主要来源。在本文中，我们着手确定附近的49个样本中的氟丰度，明亮的K-巨星，我们以前已经确定了恒星参数以及α丰度均匀的光学高分辨率光谱。氟丰度由用分光计Phoenix观察到的2.3 $μ$ m HF分子线确定。我们将氟的丰度与主要产生于II型超新星的α元素的丰度进行比较，发现氟和α元素并不同步演化，排除了II型超新星是太阳系附近氟的主要生产者。此外，我们还发现了氟相对于氧的次级行为，这是另一个证据，反对II型超新星在太阳附近氟的产生中发挥重要作用。氟的这种次级行为将对其他两个建议的生产地点的恒星模型提出新的限制：渐近巨星分支星和沃尔夫-拉叶星。
Upper limit on HF(1-0) absorption in a dusty star-forming galaxy at $z = 6$: Constraints on early fluorine enrichment
Institute of Astronomy, Graduate School of Science, The University of Tokyo（东京大学理学研究科天体物理学研究所）；Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo（东京大学前沿研究院宇宙物理与数学研究所（WPI）卡弗里研究所）；Centre for Astrophysics Research, Department of Physics, Astronomy and Mathematics, University of Hertfordshire（赫特福德大学物理、天文与数学系天体物理学研究中心）；Research Center for the Early Universe, Graduate School of Science, The University of Tokyo（东京大学理学研究科早期宇宙研究中心）；Faculty of Engineering, Hokkai-Gakuen University（北海道学园大学工学部）；Research Center for Physics and Mathematics, Osaka Electro-Communication University（大阪电通大学理数研究中心）；Institute for Advanced Research, Nagoya University（名古屋大学高等研究院）
