千新星近红外光谱中的铈特征：来自一颗化学丰度特殊星的启示
Cerium features in kilonova near-infrared spectra: implication from a chemically peculiar star
AI总结：
本文利用化学丰度特殊星HR 465的近红外光谱作为千新星光谱的实验室，证明其Ce III谱线特征与GW170817千新星中蓝移的宽吸收特征吻合，支持将该特征识别为铈。
摘要：
对中子星并合事件GW170817产生的千新星的观测，开辟了直接研究中子星并合r过程核合成的途径。然而，由于缺乏完整的原子数据，尤其是在近红外波段，识别千新星光谱中的单个元素仍然具有挑战性。在本文中，我们证明具有增强重元素丰度的化学丰度特殊星的光谱可以为我们研究千新星光谱提供一个出色的天体物理实验室。我们表明，晚期B型化学丰度特殊星HR 465的光球层具有与并合后约2.5天千新星谱线形成区域相似的镧系元素丰度和电离度。用Subaru/IRD获取的HR 465近红外光谱表明，Ce III谱线在约16,000 Å处产生最强的吸收特征，并且在这些谱线附近没有其他强度相当的跃迁。Ce III谱线与GW170817中观测到的14,500 Å处、蓝移为v=0.1c的宽吸收特征很好地吻合，这支持了Domoto等人（2022）最近将该特征识别为Ce III的结论。
英文摘要：
Observations of the kilonova from a neutron star merger event GW170817 opened a way to directly study r-process nucleosynthesis by neutron star mergers. It is, however, challenging to identify the individual elements in the kilonova spectra due to lack of complete atomic data, in particular, at near-infrared wavelengths. In this paper, we demonstrate that spectra of chemically peculiar stars with enhanced heavy element abundances can provide us with an excellent astrophysical laboratory for kilonova spectra. We show that the photosphere of a late B-type chemically peculiar star HR 465 has similar lanthanide abundances and ionization degrees with those in the line forming region in a kilonova at $\sim 2.5$ days after the merger. The near-infrared spectrum of HR 465 taken with Subaru/IRD indicates that Ce III lines give the strongest absorption features around 16,000 A and there are no other comparably strong transitions around these lines. The Ce III lines nicely match with the broad absorption features at 14,500 A observed in GW170817 with a blueshift of v=0.1c, which supports recent identification of this feature as Ce III by Domoto et al. (2022).
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