Insights from the APOKASC Determination of the Evolutionary State of Red-Giant Stars by consolidation of different methods
Yvonne Elsworth, Saskia Hekker, Jennifer A. Johnson, Thomas Kallinger, Benoit Mosser, Marc Pinsonneault, Marc Hon, James Kuszlewicz, Andrea Miglio, Aldo Serenel… 展开作者
Yvonne Elsworth, Saskia Hekker, Jennifer A. Johnson, Thomas Kallinger, Benoit Mosser, Marc Pinsonneault, Marc Hon, James Kuszlewicz, Andrea Miglio, Aldo Serenelli, Dennis Stello, Jamie Tayar, Mathieu Vrard
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19 pages, 10 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society
The internal working of low-mass stars is of great significance to both the study of stellar structure and the history of the Milky Way. Asteroseismology has the power to directly sense the internal structure of stars and allows for the determination of the evolutionary state -- i.e. has helium burning commenced or is the energy generated only by the fusion in the hydrogen-burning shell? We use observational data from red-giant stars in a combination (known as APOKASC) of asteroseismology (from the \textit{Kepler} mission) and spectroscopy (from SDSS/APOGEE). The new feature of the analysis is that the APOKASC evolutionary state determination is based on the comparison of diverse approaches to the investigation of the frequency-power spectrum. The high level of agreement between the methods is a strong validation of the approaches. Stars for which there is not a consensus view are readily identified. The comparison also facilitates the identification of unusual stars including those that show evidence for very strong coupling between p and g cavities. The comparison between the classification based on the spectroscopic data and asteroseismic data have led to a new value for the statistical uncertainty in APOGEE temperatures. These consensus evolutionary states will be used as an input for methods that derive masses and ages for these stars based on comparison of observables with stellar evolutionary models (`grid-based modeling') and as a training set for machine-learning and other data-driven methods of evolutionary state determination
Spectroscopic identification of rapidly rotating red giant stars in APOKASC-3 and APOGEE DR16
快速旋转的红巨星在天体物理学上很有趣，但很罕见。在本文中，我们提出了一个目录的3217个活跃的红巨星候选人在APOGEE DR 16调查。我们使用一个控制样本中的开普勒领域的充分研究，以证明一个强大的旋转和异常之间的关系，在光谱解决方案相对于典型的巨人。在整个调查中具有类似解决方案的明星被确定为候选人。我们使用vsin \textiti测量来确认50+/- 1.2%的候选者是确定的快速旋转者，而开普勒控制样本为4.9+/-0.2%。在开普勒控制样本和来自DR 16的控制样本中，我们发现有3-4倍于5 < vsini < 10 km s $^{-1}$ compared to vsini >10 km s $^{-1}$的巨星旋转，这是红巨星异常旋转的传统阈值。绝大多数的中间旋光子在光谱上并不是反常的。我们使用来自APOGEE和\textit{Gaia}的二元诊断来推断二元分数为73+/-2.4%。我们确定了一个显着的偏差，在报告的金属丰度的候选人与完整的光谱解决方案，与中位偏移量为0.37德克斯在[M/H]从对照样品。因此，高达10%的[M/H]<-1的恒星并不是真正的贫金属恒星。最后，我们使用盖亚数据来确定一个子人口的主序列光度双星错误地归类为巨人。
Tales of stellar and binary co-evolution, told by stellar oscillations -- Binary demographics and their impact on stellar mass, orbits, and age estimates in main-sequence and red-giant stars
Instituto de Astrofísica de Canarias（加那利天体物理研究所）；Universidad de La Laguna（拉古纳大学）
Surface brightness-color relations for red giant branch stars: Observational constraints on metallicity effects using the ARD method
Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台）；Key Laboratory for Structure and Evolution of Celestial Objects, Chinese Academy of Sciences（中国科学院天体结构与演化重点实验室）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；University of the Chinese Academy of Sciences（中国科学院大学）
Distance and extinction determination for APOGEE stars with Bayesian method
使用贝叶斯技术，我们推导出的距离和距离超过100,000红巨星观察到的阿帕奇点天文台星系演化实验（APOGEE）调查考虑到光谱的限制，从APOGEE恒星参数和光度的限制，从2 MASS，以及对银河系的先验知识。导出的距离与其他四种独立方法的距离进行了比较，即依巴谷星团，星团，APOGEE红团星，以及APOKASC（Rodrigues et al. 2014）和SAGA目录（Casagrande et al. 2014）的星震距离。这些比较涵盖了从0.02千秒差距到20千秒差距的距离尺度上的四个数量级。结果表明，我们的距离与其他方法的距离吻合得很好：我们的贝叶斯距离与其他方法的贝叶斯距离的平均相对差在-4.2%~+3.6%之间，离散度在15%~ 25%之间。对所有恒星的消光系数也被推导出来，并与其他几种独立的方法进行了比较：Rayleigh-Jeans Color Excess（RJCE）方法，Gonzalez的二维消光图，以及三维消光图和模型。比较表明，总体而言，估计的反射率非常一致，但RJCE往往高估了冷恒星和低logg天体的反射率。
