Residual Abundances in GALAH DR3: Implications for Nucleosynthesis and Identification of Unique Stellar Populations
Residual Abundances in GALAH DR3: Implications for Nucleosynthesis and Identification of Unique Stellar Populations
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DOI：
10.3847/1538-4357/ac5826
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发表时间：
2021-10
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影响因子：
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通讯作者：
Emily J. Griffith;D. Weinberg;S. Buder;Jennifer A. Johnson;James W. Johnson;F. Vincenzo
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作者：
Emily J. Griffith;D. Weinberg;S. Buder;Jennifer A. Johnson;James W. Johnson;F. Vincenzo
我们研究了82910颗来自GALAH+ DR3星系盘状恒星的16种元素的[X/Mg]丰度。我们用一个双过程模型拟合了低ia族和高ia族的中位数趋势，该模型描述了恒星的丰度，根据快速核心坍缩和延迟ia型超新星成分。对于每个样本恒星，我们拟合这两个分量的振幅，并从这两个参数拟合中计算残余Δ[X/H]丰度。我们发现已测得的元素的均方根残差指数> 0.07，一些元素（如Ba、Y和Zn）之间的相关残差表明了共同的富集源。通过对具有大残差的恒星的详细调查，我们推断出大约40%的大偏差是物理偏差，60%是由问题数据引起的，如未标记的二进制，较差的波长解和较差的大地差。作为具有独特丰度模式的一个例子，我们确定了15颗恒星，它们的Na指数增加了0.3-0.6，但从O到Ni的其他元素丰度正常，Cu, Zn， Y和Ba的平均残差为正。我们测量了14个开放团簇的中位数元素残差，发现在年轻团簇中，O、Ca、K、Y和Ba的指数系统性地提高了~ 0.1-0.4，Cu的指数减少了~ 0.2。最后，我们提出了一个限制性的三过程模型，其中我们添加了一个渐近巨型分支星（AGB）成分以更好地拟合Ba和y。通过添加第三个过程，我们确定了一个优先年轻的恒星群体，其AGB富集程度远高于SNIa富集程度。
We investigate the [X/Mg] abundances of 16 elements for 82,910 Galactic disk stars from GALAH+ DR3. We fit the median trends of low-Ia and high-Ia populations with a two-process model, which describes stellar abundances in terms of a prompt core-collapse and delayed Type-Ia supernova component. For each sample star, we fit the amplitudes of these two components and compute the residual Δ[X/H] abundances from this two-parameter fit. We find rms residuals ≲0.07 dex for well-measured elements and correlated residuals among some elements (such as Ba, Y, and Zn) that indicate common enrichment sources. From a detailed investigation of stars with large residuals, we infer that roughly 40% of the large deviations are physical and 60% are caused by problematic data such as unflagged binarity, poor wavelength solutions, and poor telluric subtraction. As one example of a population with distinctive abundance patterns, we identify 15 stars that have 0.3–0.6 dex enhancements of Na but normal abundances of other elements from O to Ni and positive average residuals of Cu, Zn, Y, and Ba. We measure the median elemental residuals of 14 open clusters, finding systematic ∼0.1–0.4 dex enhancements of O, Ca, K, Y, and Ba and ∼0.2 dex depletion of Cu in young clusters. Finally, we present a restricted three-process model where we add an asymptotic giant branch star (AGB) component to better fit Ba and Y. With the addition of the third process, we identify a population of stars, preferentially young, that have much higher AGB enrichment than expected from their SNIa enrichment.