Recent high resolution spectroscopic analysis of nearby FGK stars suggests that a high C/O ratio of greater than 0.8, or even 1.0, is relatively common. Two published catalogs find C/O$>0.8$ in 25-30% of systems, and C/O$>1.0$ in $\sim$~6-10%. It has been suggested that in protoplanetary disks with C/O$>0.8$ that the condensation pathways to refractory solids will differ from what occurred in our solar system, where C/O$=0.55$. The carbon-rich disks are calculated to make carbon-dominated rocky planets, rather than oxygen-dominated ones. Here we suggest that the derived stellar C/O ratios are overestimated. One constraint on the frequency of high C/O is the relative paucity of carbon dwarfs stars ($10^{-3}-10^{-5}$) found in large samples of low mass stars. We suggest reasons for this overestimation, including a high C/O ratio for the solar atmosphere model used for differential abundance analysis, the treatment of a Ni blend that affects the O abundance, and limitations of one-dimensional LTE stellar atmosphere models. Furthermore, from the estimated errors on the measured stellar C/O ratios, we find that the significance of the high C/O tail is weakened, with a true measured fraction of C/O$>0.8$ in 10-15% of stars, and C/O$>1.0$ in 1-5%, although these are still likely overestimates. We suggest that infrared T-dwarf spectra could show how common high C/O is in the stellar neighborhood, as the chemistry and spectra of such objects would differ compared to those with solar-like abundances. While possible at C/O$>0.8$, we expect that carbon-dominated rocky planets are rarer than others have suggested.
GLOW I: Comprehensive Measurements of Gas-Rich, Star-Forming, Low-Mass Galaxies in the Nearby Universe
Space Telescope Science Institute（太空望远镜科学研究所）；Rutgers University（罗格斯大学）；University of Utah（犹他大学）；Indiana University（印第安纳大学）；Dartmouth College（达特茅斯学院）；University of Minnesota（明尼苏达大学）；University of Washington（华盛顿大学）；Macalester College（麦卡利斯特学院）；New Mexico State University（新墨西哥州立大学）；The University of Texas at Austin（德克萨斯大学奥斯汀分校）；Cosmic Frontier Center, The University of Texas at Austin（德克萨斯大学奥斯汀分校宇宙前沿中心）；Center for Computational Astrophysics, Flatiron Institute（西蒙斯基础研究所计算天体物理中心）；University of Arizona（亚利桑那大学）；West Virginia University（西弗吉尼亚大学）
Exploring the Milky Way stellar disk. Carbon, nitrogen, oxygen, sulphur, potassium, and copper abundances for 714 F- and G-type dwarf stars in the solar neighbourhood
Space Telescope Science Institute（太空望远镜科学研究所）；Rutgers University（罗格斯大学）；University of Utah（犹他大学）；The University of Chicago（芝加哥大学）；New Mexico State University（新墨西哥州立大学）；Dartmouth College（达特茅斯学院）；University of Minnesota（明尼苏达大学）；The University of Texas at Austin（德克萨斯大学奥斯汀分校）
Identifying the chemistry of the dust around AGB stars in nearby galaxies
渐近巨星分支（AGB）星是星系星际介质化学富集的重要贡献者。因此，必须限制AGB对星系尘埃收支的贡献。最近对大麦哲伦云和小麦哲伦云的总尘埃注入率的估计（LMC和SMC; Riebel et al. 2012，Boyer et al. 2012，Srinivasan et al. in prep）使用了斯皮策太空望远镜SAGE（Surveying the Agents of Galaxy Evolution; Meixner et al. 2006）和SAGE-SMC（Gordon et al. 2011）调查的数据。当按粉尘化学分类时，这些数据可以比较富氧粉尘和含碳粉尘的产生率。例如，在大麦哲伦星系中，碳星产生尘埃的速度大约是富氧AGB的2.5倍。可靠地确定这两种尘埃的贡献率将作为化学演化模型的输入。然而，斯皮策IRAC测光带并不足以探测到中红外光谱特征，这些特征可以将富氧AGB与碳星区分开来，即9.7 $μ$ m硅酸盐特征和11.3 $μ$ m碳化硅特征。SPICA在4 - 30 $μ$ m范围内具有连续的光谱覆盖范围，因此有可能区分这两种类型的化学物质。在这篇文章中，来自AGB星模型网格的合成测光，GRAMS（Sargent et al. 2011; Srinivasan et al. 2011）将被用来讨论SPICA可能提供这项研究的科学可能性。
