论文标题
极为金属贫困的薄磁盘星2Mass J1808-5104及其起源的化学丰度模式
The chemical abundance pattern of the extremely metal-poor thin disk star 2MASS J1808-5104 and its origins
论文作者
论文摘要
我们提出了高分辨率（$ r \ sim35,000 $），高信号到噪声（$ s/n = 350 $）麦芽岩/麦克光谱极为金属贫困星2mass 2mass〜j1808 $ - $ 5104。我们发现[fe/h] = $ - $ 4.01（光谱LTE恒星参数），[fe/h] = $ - $ 3.8（光度法恒星参数），[fe/h] = $ - $ 3.7（光谱NLTE恒星恒星参数）。我们测量了CH G频段的碳与铁比为$ \ mbox {[C/Fe]} = 0.38 $。 J1808 $ - $ 5104因此不是碳增强的，与许多其他类似低铁丰度的恒星相反。我们还首次确定了钡丰度（$ \ mbox {[[ba/fe]} = -0.78 $），并获得了氮丰度的上限显着降低（[N/Fe] $ <-0.2 $）。 J1808 $ - $ 5104的低比率为$ \ mbox {[[sr/ba]} = - 0.17 $，这与超生物矮人星系中的恒星一致。我们还符合J1808 $ - 5104美元的丰度模式，其核合成从人口\，III超新星模型的网格产生。非常适合丰富的模式，建议J1808 $ - $ 5104源自一个浓缩的气体，由单个巨大的超级新星富含E $ = 10 \ times10^{51} $ \，ERG的高爆炸能量，Erg和祖先恒星质量M $ = 29.5 $ = 29.5 $ \，m $ $ _ $ _}有趣的是，J1808 $ - $ 5104是银河薄磁盘的成员，这是我们详细的运动学分析和计算出的恒星动作和速度所证实的。最后，我们还使用时间依赖的银河电位\ texttt {ortient}建立了J1808 $ - $ 5104的轨道历史。 J1808 $ - $ 5104似乎具有稳定的准圆轨道，并且很大程度上仅限于薄磁盘。这一独特的轨道历史，恒星非常老（$ \ sim13.5 $ \，gyr）以及低[c/fe]和[sr/ba]比率表明，J1808 $ - 5104可能是在最早的乳白色之路的最早时期形成的，它最有可能与原始较薄的尼尔德式组装相关。
We present a high-resolution ($R\sim35,000$), high signal-to-noise ($S/N=350$) Magellan/MIKE spectrum of the bright extremely metal-poor star 2MASS~J1808$-$5104. We find [Fe/H] = $-$4.01 (spectroscopic LTE stellar parameters), [Fe/H] = $-$3.8 (photometric stellar parameters), [Fe/H] = $-$3.7 (spectroscopic NLTE stellar parameters). We measured a carbon-to-iron ratio of $\mbox{[C/Fe]}= 0.38$ from the CH G-band. J1808$-$5104 is thus not carbon-enhanced, contrary to many other stars with similarly low iron abundances. We also determine, for the first time, a barium abundance ($\mbox{[Ba/Fe]} =-0.78$), and obtain a significantly reduced upper limit for the nitrogen abundance ([N/Fe]$ < - 0.2$). J1808$-$5104 has low ratio of $\mbox{[Sr/Ba]}=-0.17$, which is consistent with that of stars in ultra-faint dwarf galaxies. We also fit the abundance pattern of J1808$-$5104 with nucleosynthesis yields from a grid of Population\,III supernova models. There is a good fit to the abundance pattern which suggests J1808$-$5104 originated from gas enriched by a single massive supernova with a high explosion energy of E $=10\times10^{51}$\,erg and a progenitor stellar mass of M$=29.5$\,M$_{\odot}$. Interestingly, J1808$-$5104 is a member of the Galactic thin disk, as confirmed by our detailed kinematic analysis and calculated stellar actions and velocities. Finally, we also established the orbital history of J1808$-$5104 using our time-dependent Galactic potential the \texttt{ORIENT}. J1808$-$5104 appears to have a stable quasi-circular orbit and been largely confined to the thin disk. This unique orbital history, the star's very old age ($\sim13.5$\,Gyr), and the low [C/Fe] and [Sr/Ba] ratios suggest that J1808$-$5104 may have formed at the earliest epoch of the hierarchical assembly of the Milky Way, and it is most likely associated with the primordial thin disk.
