AI 中文总结
该研究提出红巨星间歇性非对称质量抛射可产生白矮星 kick，总 kick 由大量小 kick 叠加而成，还模拟了双星轨道演化，发现大间距双星可变为未束缚态，偏心率或趋近1引发恒星碰撞。
AI 中文摘要
近期观测发现证据表明，白矮星（WD）在其红巨星前身星的包层被抛射时会获得约1 km/s的 kick。我们证明这类 kick 可源于红巨星恒星的非对称且间歇性质量损失。基于红巨星质量损失的简单流体动力学模型，每次质量抛射事件可能抛射约10⁻⁴ M☉的物质，为恒星赋予一个小且随机取向的 kick，白矮星的总 kick 源于大量（N ~ 10⁴）此类事件的叠加。每次 kick 量级为vₖ ~ 5 m/s，总 kick 量级为vₖ,tot ≈ √N vₖ ~ 0.5 km/s。我们预测质量更大的白矮星会产生显著更大的净 kick。我们还对经历随机系列 kick 的双星系统的轨道演化进行建模，开发了解析模型以解释数值积分结果。对于标称质量抛射参数，间距较大的双星（a ≳ 10³ AU）可能会变为未束缚态，且间距越大、白矮星质量越高，未束缚系统的比例越大。轨道偏心率也可趋近于1，引发恒星碰撞，可能产生发光暂现源和偏心公共包层事件。
英文摘要
Recent observations have found evidence that white dwarf (WD) stars receive a kick of $\sim$1 km/s as the envelopes of their red giant progenitors are expelled. We show that these kicks can arise from asymmetric and episodic mass loss of red giant stars. Based on simple hydrodynamic models of red giant mass loss, each mass ejection event likely expels of order $\sim \! 10^{-4} \, M_\odot$, imparting a small and randomly oriented kick to the star, with the net kick to the WD arising from a combination of many $(N \sim 10^4)$ events. Each kick is of order $v_k \sim 5 \, {\rm m/s}$, with a total kick of order $v_{\rm k,tot} \approx \sqrt{N} v_k \sim 0.5 \, {\rm km/s}$. We predict substantially larger net kicks for higher mass WDs. We also model the orbital evolution of binary stars experiencing a stochastic series of kicks, developing analytic models to explain numerical integrations. For nominal mass ejection parameters, widely separated binaries $(a \gtrsim 10^3 \, {\rm AU})$ can become unbound, with larger fractions of unbound systems at larger separations and for higher WD masses. The orbital eccentricities can also approach unity, causing stellar collisions that may result in luminous transients and eccentric common envelope events.
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