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.
Differential Reddening and Extinction Law Analyses of Galactic Open Clusters
CAS Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences(中国科学院国家天文台光学天文重点实验室);School of Astronomy and Space Science, University of the Chinese Academy of Sciences(中国科学院大学天文与空间科学学院);Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University(北京师范大学天文与地球空间科学研究院)
Ultra-cool dwarfs: new discoveries, proper motions, and improved spectral typing from SDSS and 2MASS photometric colors
目标。我们试图从斯隆数字巡天(SDSS DR 7)的第七次数据发布中识别超冷矮星,SDSS i-z和r-z颜色。我们还从SDSS,2 MASS和UKIDSS获得自行数据,并从SDSS和2 MASS光度颜色改进光谱类型。方法.我们从SDSS DR 7中选择了超冷矮星候选者,新的光度选择标准是基于对已知L和T矮星的参数化研究。然后,这些物体与2微米全天巡天和UKIRT红外深空巡天第四次数据发布(UKIDSS DR 4)进行交叉识别。我们得到适当的运动约束相结合的SDSS,2 MASS,UKIDSS的位置信息。通过这种方式,我们能够在一定程度上使用多历元方法评估我们样品的可信度,这补充了光谱确认。一些自行受到短基线的影响,但是,作为一个通用的工具,这种方法提供了很大的潜力,以确认微弱的L矮星作为UKIDSS覆盖范围的增加。此外,我们得到更新的颜色光谱类型的关系L和T矮星与SDSS和2 MASS的星等。结果我们提出了59个新的附近的M和L矮星从SDSS DR 7的成像目录中选择,包括自行和光谱类型计算更新的颜色光谱类型关系。并从SDSS、2 MASS和UKIDSS中获得所有物体的自行。
New galactic star clusters discovered in the VVV survey. Candidates projected on the inner disk and bulge
VISTA Variables in the Vía Láctea(VVV)是ESO使用4米可见光和红外巡天望远镜(VISTA)进行的六次公众巡天之一。VVV巡天覆盖了银河系凸起和邻近的部分,主要目标之一是在以前无法到达的银河系模糊部分中寻找新的星团。这项工作背后的主要动机是发现和分析银河系内盘和凸起方向的遮蔽星团。使用复合JHKs彩色图像对VVV调查覆盖的内盘和凸起区域进行目视检查,以根据表观密度选择新的簇候选者。DR 1,DR 2,CASU,和PSF测光的10 × 10弧分领域集中在每个候选集群被用来构建颜色的幅度和颜色-颜色图。后续光谱的几个集群候选人的最亮的成员,以澄清其性质。我们报告发现了58个新的红外星团候选者。基本参数,如年龄,距离和金属丰度被确定为20个人口最多的集群。