Chemical Analysis of the Ultra-Faint Dwarf Galaxy Grus~II. Signature of high-mass stellar nucleosynthesis
T. T. Hansen, J. L. Marshall, J. D. Simon, T. S. Li, R. A. Bernstein, A. B. Pace, P. Ferguson, D. Q. Nagasawa, K. Kuehn, D. Carollo, M. Geha, D. James, A. Walke… 展开作者
T. T. Hansen, J. L. Marshall, J. D. Simon, T. S. Li, R. A. Bernstein, A. B. Pace, P. Ferguson, D. Q. Nagasawa, K. Kuehn, D. Carollo, M. Geha, D. James, A. Walker, H. T. Diehl, M. Aguena, S. Allam, S. Avila, E. Bertin, D. Brooks, E. Buckley-Geer, D. L. Burke, A. Carnero Rosell, M. Carrasco Kind, J. Carretero, M. Costanzi, L. N. da Costa, S. Desai, J. De Vicente, P. Doel, K. Eckert, T. F. Eifler, S. Everett, I. Ferrero, J. Frieman, J. García-Bellido, E. Gaztanaga, D. W. Gerdes, D. Gruen, R. A. Gruendl, J. Gschwend, G. Gutierrez, S. R. Hinton, D. L. Hollowood, K. Honscheid, N. Kuropatkin, M. A. G. Maia, M. March, R. Miquel, A. Palmese, F. Paz-Chinchón, A. A. Plazas, E. Sanchez, B. Santiago, V. Scarpine, S. Serrano, M. Smith, M. Soares-Santos, E. Suchyta, M. E. C. Swanson, G. Tarle, T. N. Varga, R. Wilkinson
备注：
17 pages, 6 figures, accepted for publication in ApJ
我们对超暗矮星系Grus~II巨星系分支顶部的三颗最亮的成员星进行了详细的丰度分析。与其他超暗矮星系和银河系晕中的贫金属恒星相比，所有恒星都表现出高于预期的$\mathrm{[Mg/Ca]}$比率。高质量（$\geqslant 20$ M $_\odot$）核心坍缩超新星的核合成已经被证明可以产生这种特征。这个小样本（3）星的丰度表明，天鹤座~II的化学富集可能是通过大量的高质量恒星演化发生的，并且与头重脚轻的初始质量函数框架相一致。然而，由于只有三颗恒星，不能排除丰度模式是星系早期随机化学富集的结果。这三颗恒星中最富金属的一颗，其快速中子俘获（$r$ -process）元素也有小幅增强。这颗恒星中的$r$过程元素的丰度模式与太阳系的比例$r$过程模式以及其他矮星系和银河系晕中的$r$过程增强型恒星相匹配，暗示了这些元素在一系列环境中的共同起源。所有目前提出的天体物理学站点的$r$过程元素的生产都与高质量的恒星，因此可能头重脚轻的初始质量功能的天鹤座~II将增加任何这些事件发生的可能性。银河系的$α$和$r$过程元素富集之间的时间延迟有利于中子星并合作为Grus~II中$r$过程元素的起源。
英文摘要：
We present a detailed abundance analysis of the three brightest member stars at the top of the giant branch of the ultra-faint dwarf galaxy Grus~II. All stars exhibit a higher than expected $\mathrm{[Mg/Ca]}$ ratio compared to metal-poor stars in other ultra-faint dwarf galaxies and in the Milky Way halo. Nucleosynthesis in high mass ($\geqslant 20$M$_\odot$) core-collapse supernovae has been shown to create this signature. The abundances of this small sample (3) stars suggest the chemical enrichment of Grus~II could have occurred through substantial high-mass stellar evolution and is consistent with the framework of a top-heavy initial mass function. However, with only three stars it can not be ruled out that the abundance pattern is the result of a stochastic chemical enrichment at early times in the galaxy. The most metal-rich of the three stars also possesses a small enhancement in rapid neutron-capture ($r$-process) elements. The abundance pattern of the $r$-process elements in this star matches the scaled $r$-process pattern of the solar system and $r$-process enhanced stars in other dwarf galaxies and in the Milky Way halo, hinting at a common origin for these elements across a range of environments. All current proposed astrophysical sites of $r$-process element production are associated with high-mass stars, thus the possible top-heavy initial mass function of Grus~II would increase the likelihood of any of these events occurring. The time delay between the $α$ and $r$-process element enrichment of the galaxy favors a neutron star merger as the origin of the $r$-process elements in Grus~II.
Carbon measurements in two ultra-faint dwarf galaxies: Grus II and Tucana IV
Università degli Studi di Firenze（佛罗伦萨大学）；INAF/Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；Alma Mater Studiorum, Università di Bologna（博洛尼亚大学）；INAF, Osservatorio di Astrofisica e Scienza dello Spazio（意大利国家天体物理研究所空间科学天文台）；Instituto de Astrofísica de Canarias（加那利天体物理学研究所）；Universidad de La Laguna（拉古纳大学）
Nucleosynthesis in the Accretion-induced Collapse of magnetised, Rotating White Dwarfs
ETH Zürich（苏黎世联邦理工学院）；Max-Planck-Institut für Gravitationsphysik（马克斯·普朗克引力物理研究所）；Yukawa Institute for Theoretical Physics, Kyoto University（京都大学汤川理论物理研究所）
Novae breves from magnetar giant flares: Potential probes of neutron star crusts
Peking University（北京大学）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学科维理天文与天体物理研究所）；Guangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University（广西大学物理科学与技术学院相对论天体物理重点实验室）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）
Characterization of Population III Stars with Stellar Atmosphere and Evolutionary Modeling and Predictions of their Observability with the James Webb Space Telescope
