富铀巨星的另一种形成情景：吞噬一颗类地行星
An Alternative Formation Scenario for Uranium-rich Giants: Engulfing a Earth-like Planet
AI总结：
针对九颗起源不明的富铀r过程巨星，本文提出红巨星吞噬类地行星的吸积情景，模型可解释观测铀丰度且基本不改变恒星结构与演化。
摘要：
诸如铀（U）元素之类的锕系元素通常通过快中子俘获过程（r过程）合成，该过程可发生于核心坍缩超新星或双中子星并合中。目前存在九颗展现出显著U丰度的r过程巨星，通常被称为富U巨星。然而，这些富U巨星的起源仍不明确。我们为这些富U巨星提出了另一种形成情景，即红巨星（RG）吞噬一颗类地行星。为了近似模拟RG吞噬类地行星的过程，我们采用了一种吸积模型，其中RG同化来自该行星的物质。我们的研究结果表明，这一吞噬事件能够显著增强极贫金属恒星（Z = 0.00001）表面源自类地行星的重元素含量，而其对太阳金属丰度恒星的影响相对温和。重要的是，极贫金属恒星和太阳金属丰度恒星的结构与演化性质在很大程度上均未受到影响。值得注意的是，我们的吞噬模型有效解释了已知富U巨星中观测到的U丰度。此外，RG吞噬类地行星后其表面U丰度的演化轨迹涵盖了所有已知富U巨星。因此，富U巨星由RG吞噬类地行星而形成是合理的。
英文摘要：
The actinides, such as the uranium (U) element, are typically synthesized through the rapid neutron-capture process (r-process), which can occur in core-collapse supernovae or double neutron star mergers. There exist nine r-process giant stars exhibiting conspicuousUabundances, commonly referred to as U-rich giants. However, the origins of these U-rich giants remain ambiguous. We propose an alternative formation scenario for these U-rich giants whereby a red giant (RG) engulfs an Earth-like planet. To approximate the process of a RG engulfing an Earth-like planet, we employ an accretion model wherein the RG assimilates materials from said planet. Our findings demonstrate that this engulfment event can considerably enhance the presence of heavy elements originating from Earth-like planets on the surfaces of very metal-poor stars (Z = 0.00001), while its impact on solar-metallicity stars is comparatively modest. Importantly, the structural and evolutionary properties of both very metalpoor and solar-metallicity stars remain largely unaffected. Notably, our engulfment model effectively accounts for the observed U abundances in known U-rich giants. Furthermore, the evolutionary trajectories of U abundances on the surfaces of RGs subsequent to the engulfment of Earth-like planets encompass all known U-rich giants. Therefore, it is plausible that U-rich giants are formed when a RG engulfs an Earth-like planet.
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