arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1102.2440astro-ph.SRastro-ph.GAastro-ph.HE
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激变变星的施主星演化

The Evolution of Cataclysmic Variables as Revealed by their Donor Stars

Christian Knigge, Isabelle Baraffe, Joseph Patterson

摘要:

我们重建的演化路径所遵循的激变变星(CV)从观察到的质量半径的关系,他们的施主星。在此过程中,我们更新了半经验CV施主序列的Boggge(2006),并提出了一个全面的审查CV演化和施主物理之间的联系。在校准了CV设置中使用的最先进的恒星模型后,我们将自洽的理论演化序列拟合到所观察到的施主质量和半径。在CV演化的标准模型中,周期间隙以下的AML被假设为仅由引力辐射(GR)驱动,而周期间隙以上的AML通常由Rappaport,Verbunt和Joss(1983)的磁制动处方描述。我们发现,这些配方的简单缩放版本与数据相当匹配。然而,最佳缩放因子在间隙以下为f_GR = 2.47 +/- 0.22,在间隙以上为f_MB = 0.66 +/- 0.05。结果的意义和应用包括:(1)修正的演化序列给出了CV最小周期和周期间隔上沿的正确位置,而标准序列则不能。(2)预测和观察到的WD温度的比较表明,甚至更高的值f_GR,但这是敏感的假设WD质量。(3)由我们的序列预测的绝对供体幅度可以用于设置到CV的距离的严格下限。(4)标准和修订的序列预测,短周期CV应该容易受到矮新星(DN)爆发,与观测一致。然而,这两个序列也预测,DNe分数之间的长周期CV应下降与P_orb。观察结果表明相反的行为。(5)对于修订后的序列,长周期CV与短周期、反弹前CV的比率比标准序列高约3倍。这可能解决CV进化中的一个长期存在的问题。[删节]

英文摘要:

We reconstruct the evolutionary path followed by cataclysmic variables (CVs) from the observed mass-radius relationship of their donor stars. Along the way, we update the semi-empirical CV donor sequence of Knigge (2006) and present a comprehensive review of the link between CV evolution and donor physics. After calibrating state-of-the art stellar models for use in the CV setting, we fit self-consistent theoretical evolution sequences to the observed donor masses and radii. In the standard model of CV evolution, AML below the period gap is assumed to be driven solely by gravitational radiation (GR), while AML above the gap is usually described by a magnetic braking prescription due to Rappaport, Verbunt & Joss (1983). We find that simple scaled versions of these recipes match the data quite well. However, the optimal scaling factors turn out to be f_GR = 2.47 +/- 0.22 below the gap and f_MB = 0.66 +/- 0.05 above. The implications and applications of our results include: (1) The revised evolution sequence yields correct locations for the CV minimum period and the upper edge of the period gap; the standard sequence does not. (2) A comparison of predicted and observed WD temperatures suggests an even higher value for f_GR, but this is sensitive to the assumed WD mass. (3) The absolute donor magnitudes predicted by our sequences can be used to set firm lower limits on the distances toward CVs. (4) Both standard and revised sequences predict that short-period CVs should be susceptible to dwarf nova (DN) eruptions, consistent with observations. However, both sequences also predict that the DNe fraction among long-period CVs should decline with P_orb. Observations suggest the opposite behaviour. (5) The ratio of long-period CVs to short-period, pre-bounce CV is about 3x higher for the revised sequence than the standard one. This may resolve a long-standing problem in CV evolution. [abridged]

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