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arXiv 2202.08852astro-ph.SR
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过接触双星的建模,我。潮汐形变效应

Modeling overcontact binaries, I. The effect of tidal deformation

M. Fabry, P. Marchant, H. Sana

摘要:

在大质量恒星的领域,强烈的双星相互作用是很常见的。一个极端的例子是过接触系统,它被认为是所有恒星向合并演化的一部分,并被假设在双黑洞的形成中发挥作用。然而,重要的简化模型的演变过接触双星,即潮汐或旋转变形经常被忽略。然而,观测和理论都表明,过度接触的恒星会发生严重的潮汐变形,从而对模型中未考虑的外层产生潜在的重要影响。在这项工作中,我们开发的方法来表示潮汐变形的恒星。利用数值方法,计算了双星Roche势对一维球面恒星结构方程的结构修正因子,并与已有结果和单旋转恒星的结构修正进行了比较.我们将新的结构修正因子应用到恒星演化程序MESA中,并对几个实例进行了研究。我们比较我们的模拟之间的差异时,不包括旋转,当我们处理旋转使用单星校正(即只占离心变形)或当我们使用潮汐变形。我们发现,忽略旋转变形分离食双星可以产生一个半径差异高达5%。潮汐和单星离心畸变模型之间的差异是更良性的1%,表明单旋转星模型是一个合适的近似潮汐变形的恒星在一个双星系统。在overcontact配置,我们发现一个类似的5%的变化,表面特性作为潮汐扭曲的结果,相对于非旋转模型,这表明它是不合适的模型双星,填补他们的洛希瓣显着,作为非旋转。

英文摘要:

In the realm of massive stars, strong binary interaction is commonplace. One extreme case are overcontact systems, which is expected to be part of the evolution of all stars evolving towards a merger, and is hypothesized to play a role in the formation of binary black holes. However, important simplifications are made to model the evolution of overcontact binaries, namely that tidal or rotational deformation is frequently ignored. Yet, both observation and theory show that overcontact stars are heavily tidally deformed, leaving a potentially important effect on the outer layers unaccounted for in models. In this work we develop the methodology to represented tidally deformed stars. Using numerical methods, we compute the structure correction factors to the 1D spherical stellar structure equations due to the binary Roche potential, and compare them to existing results and the structure corrections of single rotating stars. We implement the new structure correction factors into the stellar evolution code MESA and explore several case studies. We compare the differences between our simulations when no rotation is included, when we treat rotation using single star corrections (i.e. only accounting for centrifugal deformation) or when we use tidal deformation. We find that ignoring rotation in deformed detached eclipsing binaries can produce a radius discrepancy of up to 5%. The difference between tidal and single star centrifugal distortion models is more benign at 1%, showing that single rotating star models are a suitable approximation of tidally deformed stars in a binary system. In overcontact configurations, we find a similar 5% variation in surface properties as a result of tidal distortion with respect to non-rotating models, showing that it is inappropriate to model binary stars that fill their Roche lobe significantly, as non-rotating.

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