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arXiv 1107.4029astro-ph.SRastro-ph.GA
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银河系S星:颜色、运动和光谱特征的研究

Galactic S Stars: Investigations of Color, Motion, and Spectral Features

Elizabeth Otto, Paul J Green, Richard O. Gray

摘要:

已知的亮S星,通过它们增强的s-过程丰度和C/O比来识别,通常是渐近巨星分支(AGB)或红巨星分支(RGB)的成员。这些天体的现代数字光谱很少被公布,从中可以得出中等分辨率的光谱指数和分类。对于已发表的S星,我们使用两微米全天巡天(2 MASS)找到准确的位置,并使用Tillinghast反射器的FAST摄谱仪。霍普金斯获得57个物体的光谱。我们提供了一个数字化的S星光谱图集,包括14个光谱的S星不同的光谱特征。我们定义并推导出基本的光谱指数,可以帮助区分晚型(M)巨星和碳星的S星。我们卷积我们所有的光谱与SDSS的带通,并采用由此产生的gri幅度与2 MASS JHK磁一起调查S星的颜色。S星的颜色类似于碳星和M星,因此很难单独通过颜色来区分。利用IRAS和AKARI的近红外和中红外颜色,我们将一些恒星识别为内在的(AGB)或外在的(过去的质量转移增强了丰度)。我们还使用V波段和2 MASS星等来计算样本中恒星的温度指数。我们分析了样本恒星的自行和弛豫,以确定绝对星等和距离的上限和下限,并确认大多数可能是巨星。

英文摘要:

Known bright S stars, recognized as such by their enhanced s-process abundances and C/O ratio, are typically members of the asymptotic giant branch (AGB) or the red giant branch (RGB). Few modern digital spectra for these objects have been published, from which intermediate resolution spectral indices and classifications could be derived. For published S stars we find accurate positions using the Two-Micron All Sky Survey (2MASS), and use the FAST spectrograph of the Tillinghast reflector on Mt. Hopkins to obtain the spectra of 57 objects. We make available a digital S star spectral atlas consisting of 14 spectra of S stars with diverse spectral features. We define and derive basic spectral indices that can help distinguish S stars from late-type (M) giants and carbon stars. We convolve all our spectra with the SDSS bandpasses, and employ the resulting gri magnitudes together with 2MASS JHK mags to investigate S star colors. S stars have colors similar to carbon and M stars, and are therefore difficult to distinguish by color alone. Using near and mid-infrared colors from IRAS and AKARI, we identify some of the stars as intrinsic (AGB) or extrinsic (with abundances enhanced by past mass-transfer). We also use V band and 2MASS magnitudes to calculate a temperature index for stars in the sample. We analyze the proper motions and parallaxes of our sample stars to determine upper and lower limit absolute magnitudes and distances, and confirm that most are probably giants.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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