On the alpha-element gradients of the Galactic thin disk using Cepheids
K. Genovali, B. Lemasle, R. da Silva, G. Bono, M. Fabrizio, M. Bergemann, R. Buonanno, I. Ferraro, P. François, G. Iannicola, L. Inno, C. D. Laney, R. -P. Kudri… 展开作者
K. Genovali, B. Lemasle, R. da Silva, G. Bono, M. Fabrizio, M. Bergemann, R. Buonanno, I. Ferraro, P. François, G. Iannicola, L. Inno, C. D. Laney, R. -P. Kudritzki, N. Matsunaga, M. Nonino, F. Primas, M. Romaniello, M. A. Urbaneja, F. Thévenin
We present new homogeneous measurements of Na, Al and three alpha-elements (Mg, Si, Ca) for 75 Galactic Cepheids. The abundances are based on high spectral resolution (R ~ 38,000) and high signal-to-noise ratio (S/N ~ 50-300) spectra collected with UVES at ESO VLT. The current measurements were complemented with Cepheid abundances either provided by our group (75) or available in the literature, for a total of 439 Galactic Cepheids. Special attention was given in providing a homogeneous abundance scale for these five elements plus iron (Genovali et al. 2013, 2014). In addition, accurate Galactocentric distances (RG) based on near-infrared photometry are also available for all the Cepheids in the sample (Genovali et al. 2014). They cover a large fraction of the Galactic thin disk (4.1 <= RG <= 18.4 kpc). We found that the above five elements display well defined linear radial gradients and modest standard deviations over the entire range of RG. Moreover, the [element/Fe] abundance ratios are constant across the entire thin disk; only the Ca radial distribution shows marginal evidence of a positive slope. These results indicate that the chemical enrichment history of iron and of the quoted five elements has been quite similar across the four quadrants of the Galactic thin disk. The [element/Fe] ratios are also constant over the entire period range. This empirical evidence indicates that the chemical enrichment of Galactic Cepheids has also been very homogenous during the range in age that they cover (~10-300 Myr). Once again, [Ca/Fe] vs. log(P) shows a (negative) gradient, being underabundant among youngest Cepheids. Finally, we also found that Cepheid abundances agree quite well with similar abundances for thin and thick disk dwarf stars and they follow the typical Mg-Al and Na-O correlations.
Understanding the dynamical structure of pulsating stars: The center-of-mass velocity and the Baade-Wesselink projection factor of the beta-Cephei star alpha-Lupi
Toward a Comprehensive Grid of Cepheid Models with MESA II. Impact of Physical and Numerical Assumptions on Elemental Abundances
Nicolaus Copernicus Astronomical Centre, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文学中心）；Space sciences, Technologies and Astrophysics Research (STAR) Institute, Université de Liège（列日大学空间科学、技术与天体物理研究（STAR）研究所）
Classical Cepheids in the Galactic thin disk I. Abundance gradients via non-local thermodynamic equilibrium spectral analysis
Università di Roma Tor Vergata（罗马第二大学）；INAF – Osservatorio Astronomico di Roma（罗马天文台）；The University of Texas at Austin（德克萨斯大学奥斯汀分校）；ASI - Space Science Data Center（意大利航天局空间科学数据中心）；University of Hawai’i at Manoa（夏威夷大学马诺阿分校）；INAF – Osservatorio Astrofisico di Torino（都灵天文台）；Texas Christian University（得克萨斯基督教大学）；INAF -- Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（博洛尼亚天文物理与空间科学观测站）；Sapienza Università di Roma（罗马第一大学）；INAF - Osservatorio Astronomico di Capodimonte（卡波迪蒙特天文台）；Parthenope University of Naples（那不勒斯帕泰诺佩大学）；Università degli Studi di Bologna（博洛尼亚大学）；The University of Tokyo（东京大学）；Universidad de La Laguna（拉古纳大学）；Odessa National University（敖德萨国立大学）
凌日系外行星调查卫星（TESS）已经开始发现附近冷亮恒星周围最终会有数千颗系外行星。这些潜在的宿主恒星必须得到很好的理解，才能在个体和种群水平上准确地描述系外行星。我们使用来自Gaia DR 2，APOGEE，GALAH，RAVE，LAMOST的调查数据和SkyMapper的光度导出的恒星特性，列出了TESS候选目标列表中2，218，434颗恒星的化学运动学特性目录。我们计算了这些恒星的运动学薄盘、厚盘和晕成员概率，发现尽管大多数TESS目标位于薄盘中，但其中4%位于厚盘中，<1%位于晕中。我们样本中的TESS感兴趣对象也显示了来自薄盘、厚盘和晕的类似贡献，其中大部分在薄盘中。我们还探讨了金属丰度和[α/Fe]分布的每个银河系的组成部分，并表明，每个交叉匹配的调查表现出金属丰度和[α/Fe]分布函数，峰值从高到低的金属丰度和低到高的[α/Fe]从薄盘的晕。这个目录将有助于探索行星的出现率，除其他事项外，关于运动学，组件成员，金属丰度，或[阿尔法/铁]。
