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arXiv 1601.08083astro-ph.SR
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大质量双星中过去质量交换事件的观测特征:HD 149 404

Observational signatures of past mass-exchange episodes in massive binaries: The case of HD 149 404

F. Raucq, G. Rauw, E. Gosset, Y. Nazé, L. Mahy, A. Hervé, F. Martins

摘要:

近距离大质量双星中的质量和动量交换在它们的演化中起着重要作用,并产生了几个观测特征,如异步旋转和改变的化学成分,这些特征在恒星再次分离后仍然存在。我们研究了分离的大质量O星双星HD 149404(O7.5If + ON9.7I,P = 9.81天)的这些影响,这被认为是经历了过去的情节情况下A罗奇叶溢出(RLOF)。使用相位分辨光谱学,我们进行了两颗恒星的光谱解纠缠。然后用CMFGEN模型大气代码分析重建的初级和次级光谱,以确定恒星参数,如有效温度和表面重力,并限制组分的化学组成。我们补充了光学研究与IUE光谱的研究,我们比较合成的二元光谱。恒星的性质与进化模型进行了比较。我们证实了一个强大的过剩的氮($\left[\rm N/C\right]\sim150\left[\rm N/C\right]_{\odot}$)的第二和轻微的氮过剩($\left[\rm N/C\right]\sim5\left[\rm N/C\right]_{\odot}$)的主星。比较这两颗恒星,我们发现了异步旋转的证据,旋转周期比为$0.50 \pm 0.11$。HD 149404中的一个过去的案例A RLOF相互作用的假设是最合理的,以解释其化学丰度和旋转双折射性。一些观察到的属性,如丰度模式,显然是一个挑战,目前的情况下,二元演化模型,但是。

英文摘要:

Mass and momentum exchanges in close massive binaries play an important role in their evolution, and produce several observational signatures such as asynchronous rotation and altered chemical compositions, that remain after the stars detach again. We investigated these effects for the detached massive O-star binary HD 149404 (O7.5If + ON9.7I, P = 9.81 days), which is thought to have experienced a past episode of case A Roche-lobe overflow (RLOF). Using phase-resolved spectroscopy, we performed the disentangling of the optical spectra of the two stars. The reconstructed primary and secondary spectra were then analysed with the CMFGEN model atmosphere code to determine stellar parameters, such as the effective temperatures and surface gravities, and to constrain the chemical composition of the components. We complemented the optical study with the study of IUE spectra, which we compare to the synthetic binary spectra. The properties of the stars were compared to evolutionary models. We confirmed a strong overabundance in nitrogen ($\left[\rm N/C\right]\sim150\left[\rm N/C\right]_{\odot}$) for the secondary and a slight nitrogen overabundance ($\left[\rm N/C\right]\sim5\left[\rm N/C\right]_{\odot}$) for the primary star. Comparing the two stars, we found evidence for asynchronous rotation, with a rotational period ratio of $0.50 \pm 0.11$. The hypothesis of a past case A RLOF interaction in HD 149404 is most plausible to explain its chemical abundances and rotational asynchronicity. Some of the observed properties, such as the abundance pattern, are clearly a challenge for current case A binary evolution models, however.

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