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arXiv 1609.02735astro-ph.SR
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大质量双星HD152218的拱点运动

Apsidal motion in the massive binary HD152218

G. Rauw, S. Rosu, A. Noels, L. Mahy, J. H. M. M. Schmitt, M. Godart, M. -A. Dupret, E. Gosset

摘要:

大质量双星系统是研究大质量恒星性质和恒星物理的重要实验室。在此背景下,我们分析了年轻的疏散星团NGC 6231中的偏心短周期早型双星HD 152218的光谱学和光度学。我们用分离码重建了单个恒星的光谱。然后将单个光谱与CMFGEN模型大气代码获得的合成光谱进行比较。我们进一步分析了双星的光变曲线,并利用它来限制轨道倾角,并得出绝对质量为19.8 +/- 1.5和15.0 +/- 1.1太阳质量。结合60多年来的径向速度测量结果,我们证明该系统以(2.04 ± 23 - 24)度/年的速率表现出拱点运动。求解Clairau-Radau方程,我们使用恒星演化模型,得到与CLES代码,计算内部结构常数和评估的理论预测的拱点运动速率作为恒星年龄和初级质量的函数。通过这种方式,我们确定HD 152218的年龄为5.8 +/- 0.6百万年,这接近于NGC 6231的大质量恒星群体的年龄范围的高端,但与等时线拟合确定的年龄范围相一致。

英文摘要:

Massive binary systems are important laboratories in which to probe the properties of massive stars and stellar physics in general. In this context, we analysed optical spectroscopy and photometry of the eccentric short-period early-type binary HD 152218 in the young open cluster NGC 6231. We reconstructed the spectra of the individual stars using a separating code. The individual spectra were then compared with synthetic spectra obtained with the CMFGEN model atmosphere code. We furthermore analysed the light curve of the binary and used it to constrain the orbital inclination and to derive absolute masses of 19.8 +/- 1.5 and 15.0 +/- 1.1 solar masses. Combining radial velocity measurements from over 60 years, we show that the system displays apsidal motion at a rate of (2.04^{+.23}_{-.24}) degree/year. Solving the Clairaut-Radau equation, we used stellar evolution models, obtained with the CLES code, to compute the internal structure constants and to evaluate the theoretically predicted rate of apsidal motion as a function of stellar age and primary mass. In this way, we determine an age of 5.8 +/- 0.6 Myr for HD 152218, which is towards the higher end of, but compatible with, the range of ages of the massive star population of NGC 6231 as determined from isochrone fitting.

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