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arXiv 2009.08658astro-ph.SR
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大质量双星HD 152248的拱点运动--对恒星内部结构的制约

Apsidal motion in the massive binary HD 152248 -- Constraining the internal structure of the stars

S. Rosu, A. Noels, M. -A. Dupret, G. Rauw, M. Farnir, S. Ekström

摘要:

大质量偏心双星的拱点运动提供了有关恒星内部结构的宝贵信息。这对于由两颗几乎相同的恒星组成的孪生双星来说尤其如此。我们利用潮汐引起的拱点运动的孪生二进制HD 152248推断构成这个系统的O7.5 III-II型恒星的内部结构的约束。我们建立恒星演化模型的代码克莱斯假设不同的处方内发生的内部混合的恒星。我们确定的模型,最好地再现观测确定的HD 152248的组件,以及他们的$k_2$,拱点运动速率的今天的属性系统。我们分析了一些约束不佳的输入参数,包括超调,湍流扩散和金属丰度的影响。我们进一步建立“单”和“二进制”GENEC模型,占恒星旋转调查的影响,二进制和旋转。我们讨论了一些影响,可能会导致我们的解释拱线运动的内部结构常数。再现观测到的$k_2$值和拱点运动速率与其他恒星参数同时需要大量的内部混合或增强的质量损失。结果表明,单星演化模型足以描述这个双星系统内部的物理。定性地说,再现观测所需的高湍流扩散可以部分归因于恒星旋转。拱线运动中的高阶项可以忽略不计。只有非常严重的旋转轴不对准才能显著影响拱点运动的速率,但在这样的双星系统中,如此高的不对准是极不可能的。我们推断的年龄估计$5.15\pm0.13$ MYR的二进制和初始质量的$32.8\pm0.6$ M $_\odot$的两颗恒星。

英文摘要:

Apsidal motion in massive eccentric binaries offers precious information about the internal structure of the stars. This is especially true for twin binaries consisting of two nearly identical stars. We make use of the tidally induced apsidal motion in the twin binary HD152248 to infer constraints on the internal structure of the O7.5 III-II stars composing this system. We build stellar evolution models with the code Clés assuming different prescriptions for the internal mixing occurring inside the stars. We identify the models that best reproduce the observationally determined present-day properties of the components of HD152248, as well as their $k_2$, and the apsidal motion rate of the system. We analyse the impact of some poorly constrained input parameters, including overshooting, turbulent diffusion, and metallicity. We further build 'single' and 'binary' GENEC models that account for stellar rotation to investigate the impacts of binarity and rotation. We discuss some effects that could bias our interpretation of the apsidal motion in terms of the internal structure constant. Reproducing the observed $k_2$ value and rate of apsidal motion simultaneously with the other stellar parameters requires a significant amount of internal mixing or enhanced mass-loss. The results suggest that a single-star evolution model is sufficient to describe the physics inside this binary system. Qualitatively, the high turbulent diffusion required to reproduce the observations could be partly attributed to stellar rotation. Higher-order terms in the apsidal motion are negligible. Only a very severe misalignment of the rotation axes could significantly impact the rate of apsidal motion, but such a high misalignment is highly unlikely in such a binary system. We infer an age estimate of $5.15\pm0.13$ Myr for the binary and initial masses of $32.8\pm0.6$ M$_\odot$ for both stars.

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