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arXiv 1709.08682astro-ph.HEastro-ph.SR
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由两个双星组成的四重系统的动力学:恒星、白矮星和Ia超新星的意义

Dynamics of Quadruple Systems Composed of Two Binaries: Stars, White Dwarfs, and Implications for Ia Supernovae

Xiao Fang, Todd A. Thompson, Christopher M. Hirata

摘要:

[摘要]我们研究了由两个四极和八极双星组成的四重系统在扰动哈密顿量下的长期动力学和Lidov-Kozai(LK)偏心率振荡。我们发现,在更广泛的参数空间范围内,相对于三重系统,系统达到高偏心率的分数得到增强。我们表明,这部分增长随着时间的推移,不像三重系统在四极顺序。这从根本上是因为它们的额外的自由度,四极系统没有一个最大的一组运动的交换常数,即使在四极阶的长期理论。我们讨论这些结果的背景下,恒星和白矮星-白矮星(WD)的双星,重点是WD WD合并和碰撞有关的Ia型超新星的问题。对于恒星-恒星系统,我们发现超过30%的系统在哈勃时间内达到高偏心率,可能通过恒星合并或近距离双星形成三重系统。对于WD-WD系统,考虑到广义相对论和潮汐的岁差和耗散,我们表明,合并率在四重系统中相对于三重系统增强了3.5 - 10倍,并且四重系统的长期演化导致合并和碰撞的延迟时间分布~1/t。在GW驱动的合并紧凑的对象,我们分类的合并,其在相空间中的演化模式,并确定了一个制度,在约8%的轨道收缩合并,偏心振荡发生在广义相对论进动时标,而不是更长的LK时标。最后,我们推广以前的治疗振荡的内二进制偏心偏心的相互轨道。我们评估的合并率在四重和三重系统和它们的生存能力的影响,恒星合并和超新星Ia的祖先。

英文摘要:

[Abridged]We investigate the long-term secular dynamics and Lidov-Kozai(LK) eccentricity oscillations of quadruple systems composed of two binaries at quadrupole and octupole order in the perturbing Hamiltonian. We show that the fraction of systems reaching high eccentricities is enhanced relative to triple systems, over a broader range of parameter space. We show that this fraction grows with time, unlike triple systems evolved at quadrupole order. This is fundamentally because with their additional degrees of freedom, quadruple systems do not have a maximal set of commuting constants of the motion, even in secular theory at quadrupole order. We discuss these results in the context of star-star and white dwarf-white dwarf(WD) binaries, with emphasis on WD-WD mergers and collisions relevant to the Type Ia supernova problem. For star-star systems, we find that more than 30% of systems reach high eccentricity within a Hubble time, potentially forming triple systems via stellar mergers or close binaries. For WD-WD systems, taking into account general relativistic and tidal precession and dissipation, we show that the merger rate is enhanced in quadruple systems relative to triple systems by a factor of 3.5-10, and that the long-term evolution of quadruple systems leads to a delay-time distribution ~1/t for mergers and collisions. In GW-driven mergers of compact objects, we classify the mergers by their evolutionary patterns in phase space and identify a regime in ~8% of orbital shrinking mergers, where eccentricity oscillations occur on the general relativistic precession timescale, rather than the much longer LK timescale. Finally, we generalize previous treatments of oscillations in the inner binary eccentricity to eccentric mutual orbits. We assess the merger rate in quadruple and triple systems and the implications for their viability as progenitors of stellar mergers and SNe Ia.

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