Testing asteroseismology with Gaia DR2: hierarchical models of the Red Clump
Testing asteroseismology with Gaia DR2: hierarchical models of the Red Clump
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DOI：
10.1093/mnras/stz1092
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发表时间：
2019-04
影响因子：
4.8
通讯作者：
O. Hall;G. Davies;Y. Elsworth;A. Miglio;T. Bedding;Anthony G. A. Brown;Saniya Khan;K. Hawkins
中科院分区：
文献类型：
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作者：
O. Hall;G. Davies;Y. Elsworth;A. Miglio;T. Bedding;Anthony G. A. Brown;Saniya Khan;K. Hawkins
天文地震学提供了与距离无关的基本恒星参数，但要经过系统学的校准。盖亚DR 2为10亿颗恒星提供了视差，这些恒星被视差零点抵消。红丛星（RC）的光度分布很窄，因此可以作为标准烛光来校准这些系统。这项工作测量了开普勒场中RC的大小和传播如何受到地震学温度和标度关系变化的影响，以及盖亚视差零点的变化。我们使用的样本5576 RC星通过asteroseismology分类。我们采用分层贝叶斯潜变量模型，发现人口水平的RC与地震学的属性，并使用这些作为先验盖亚视差零点偏移。然后，我们使用公布的零点值找到RC的位置。我们发现一个地震温度不敏感的传播RC的~0.03 mag的2 MASS K带和一个更大的和轻微的温度依赖的传播~0.13 mag的盖亚G带。K波段的本征色散为RC星提供了~1%的距离精度。仅使用盖亚数据，我们发现平均零点为-41 $\pm $10 $\mu$as。这个偏移量产生的RC绝对星等为-1.634 $\pm $0.018（K）和0.546 $\pm $0.016（G）.通过地震学获得这些相同的值将需要全球温度漂移~-70 K，这与光谱学中已知的系统学是兼容的。
Asteroseismology provides fundamental stellar parameters independent of distance, but subject to systematics under calibration. Gaia DR2 has provided parallaxes for a billion stars, which are offset by a parallax zero-point. Red Clump (RC) stars have a narrow spread in luminosity, thus functioning as standard candles to calibrate these systematics. This work measures how the magnitude and spread of the RC in the Kepler field are affected by changes to temperature and scaling relations for seismology, and changes to the parallax zero-point for Gaia. We use a sample of 5576 RC stars classified through asteroseismology. We apply hierarchical Bayesian latent variable models, finding the population level properties of the RC with seismology, and use those as priors on Gaia parallaxes to find the parallax zero-point offset. We then find the position of the RC using published values for the zero-point. We find a seismic temperature insensitive spread of the RC of ~0.03 mag in the 2MASS K band and a larger and slightly temperature-dependent spread of ~0.13 mag in the Gaia G band. This intrinsic dispersion in the K band provides a distance precision of ~1% for RC stars. Using Gaia data alone, we find a mean zero-point of -41 $\pm$ 10 $\mu$as. This offset yields RC absolute magnitudes of -1.634 $\pm$ 0.018 in K and 0.546 $\pm$ 0.016 in G. Obtaining these same values through seismology would require a global temperature shift of ~-70 K, which is compatible with known systematics in spectroscopy.