Abundance analysis of barium and mild barium stars
Abundance analysis of barium and mild barium stars
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DOI：
10.1051/0004-6361:20065867
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发表时间：
2007-02
影响因子：
6.5
通讯作者：
R. Smiljanic;G. P. D. Mello;L. D. Silva
中科院分区：
文献类型：
--
作者：
R. Smiljanic;G. P. D. Mello;L. D. Silva
目标。我们比较并讨论了正常巨星，温和钡星和钡星的丰度和趋势，寻找钡星和温和钡星之间的差异和相似之处，这可能有助于阐明这些类似物体的起源。此外，我们寻找核合成的影响可能与s-过程中观察到的文献中的元素，如铜在其他类型的s-过程丰富的恒星。方法.高信号噪声，高分辨率光谱的正常，温和的钡，钡巨人的样品获得。大气参数由Fe I和Fell线确定。Na、Mg、Al、Si、Ca、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Sr、Y、Zr、Ba、La、Ce、Nd、Sm、Eu和Gd的丰度是以红巨星∈ Vir为标准星星，通过微分分析中的等效宽度和模型大气确定的。结果钡星和温和钡星的s过程丰度的不同水平，较早被认为与恒星金属丰度有关。与这一建议相反，我们在这项工作中发现没有证据表明钡和轻钡具有不同的金属丰度范围。然而，比较重，轻s过程元素的丰度比，我们发现一些证据表明，他们不共享相同的中子照射参数。控制这种差异的确切机制仍然不清楚。作为这种分析的副产品，我们确定了两个正常的红巨星被错误地归类为温和的钡星。这一发现的相关性进行了讨论。关于建议的核合成效应可能与s过程有关，对于Cu，Mn，V和Sc等元素，我们在这里分析的任何s过程富集的恒星中没有发现异常行为的证据。然而，仍需要进一步的工作，因为其他s过程富集的物体存在明确的[Cu/Fe]与[Ba/Fe]比值关系。
Aims. We compare and discuss abundances and trends in normal giants, mild barium, and barium stars, searching for differences and similarities between barium and mild barium stars that could help shed some light on the origin of these similar objects. Also, we search for nucleosynthetic effects possibly related to the s-process that were observed in the literature for elements like Cu in other types of s-process enriched stars. Methods. High signal to noise, high resolution spectra were obtained for a sample of normal, mild barium, and barium giants. Atmospheric parameters were determined from the Fe I and Fell lines. Abundances for Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, Eu, and Gd, were determined from equivalent widths and model atmospheres in a differential analysis, with the red giant ∈ Vir as the standard star. Results. The different levels of s-process overabundances of barium and mild barium stars were earlier suggested to be related to the stellar metallicity. Contrary to this suggestion, we found in this work no evidence of barium and mild barium having a different range in metallicity. However, comparing the ratio of abundances of heavy to light s-process elements, we found some evidence that they do not share the same neutron exposure parameter. The exact mechanism controlling this difference is still not clear. As a by-product of this analysis we identify two normal red giants misclassified as mild barium stars. The relevance of this finding is discussed. Concerning the suggested nucleosynthetic effects possibly related to the s-process, for elements like Cu, Mn, V and Sc, we found no evidence for an anomalous behavior in any of the s-process enriched stars analyzed here. However, further work is still needed since a clear [Cu/Fe] vs. [Ba/Fe] anticorrelation exists for other s-process enriched objects.