The proper motions of 15 nearby（d 〈 1 kpc） open clusters（OCs） were recalculated using data from the UCAC4 catalog. Only evolved or main sequence stars inside a certain radius from the center of the cluster were u...The proper motions of 15 nearby（d 〈 1 kpc） open clusters（OCs） were recalculated using data from the UCAC4 catalog. Only evolved or main sequence stars inside a certain radius from the center of the cluster were used. The results significantly differ from the ones presented by Dias et al.（2014）. This could be explained by a different approach in which we take the field star contamination into account. The present work aims to emphasize the importance of applying photometric criteria for the calculation of OC proper motions.展开更多
We quantify and correct systematic errors in PPMXL proper motions using extragalactic sources from the first two LAMOST data releases and the Vbron-Cetty ＆ Vebron Catalog of Quasars. Although the majority of the sour...We quantify and correct systematic errors in PPMXL proper motions using extragalactic sources from the first two LAMOST data releases and the Vbron-Cetty ＆ Vebron Catalog of Quasars. Although the majority of the sources are from the Veron catalog, LAMOST makes important contributions in regions that are not well-sampled by previous catalogs, particularly at low Galactic latitudes and in the south Galactic cap. We show that quasars in PPMXL have measurable and significant proper motions, which reflect the systematic zero-point offsets present in the catalog. We confirm the global proper motion shifts seen by Wu et al., and additionally find smaller-scale fluctuations of the QSO-derived corrections to an absolute frame. We average the proper motions of 158 106 extragalactic objects in bins of 3° ×3° and present a table of proper motion corrections.展开更多
Analyzing Hipparcos proper motions of 1352 O B5 stars, we have found a clear stellar warping motion that is a systematic rotation +3 8±1 1 kms -1 kpc -1 of stars about the axis pointing to the galactic center in ...Analyzing Hipparcos proper motions of 1352 O B5 stars, we have found a clear stellar warping motion that is a systematic rotation +3 8±1 1 kms -1 kpc -1 of stars about the axis pointing to the galactic center in the sense of increasing the inclination of the HI warp, and a remarkably large galactic rotation of (V 0) O-B5 = 268 7 ± 11 9kms -1 , compared with the IAU recommendation (V 0 = 220 ± 20kms -1 ), given the galactocentric distance of the sun R 0 = 8 5kpc. Combining Hipparcos proper motions and the radial velocity data, we have then studied the kinematics for 151 classical cepheids. The results show a contracting motion of the Galaxy in the solar neibourhood, V θ/θ/R =-2 60 ± 1 07kms -1 kps -1 , which is along the solar circle. In the present paper, we have also analyzed proper motions of 21000 K-M giants, and again we found a large galactic rotation (V 0) K-M = 252 6±9 5kms -1 .展开更多
We examine 14 plates of the globular cluster M3 (NGC 5272) taken with the 40 cm refractor at the Sheshan station of Shanghai Astronomical Observatory. The plates span over a period of about 77 years. The positions and...We examine 14 plates of the globular cluster M3 (NGC 5272) taken with the 40 cm refractor at the Sheshan station of Shanghai Astronomical Observatory. The plates span over a period of about 77 years. The positions and absolute proper motions of eight stars in the Hipparcos Catalogue and of 49 stars in the Tycho-2 Catalogue are used as the reference frame. The astrometric reduction is made with the central overlapping principle. The absolute proper motions of 534 stars in a region of about 100' × 100' around the cluster are measured. With the new proper motion data the membership probabilities of the stars are determined. The average absolute proper motion obtained for the cluster is -0.06±0.30 mas yr-1 in R.A. and -2.6±0.30 mas yr-1 in Decl. By combining this result with the known distance and radial velocity of the cluster, we also obtained the Galactic orbit of M3 for a chosen three-component Galactic potential.展开更多
We have obtained the absolute proper motion of globular cluster M3 from measurements of 14 plates taken with the 40cm refractor at Sheshan station of Shanghai observatory, spanning epoch is about 80 years. The positio...We have obtained the absolute proper motion of globular cluster M3 from measurements of 14 plates taken with the 40cm refractor at Sheshan station of Shanghai observatory, spanning epoch is about 80 years. The positions and absolute proper motions of 24 stars in ACT catalogue are used as the reference frame. The reduction was made with the central overlapping principle. The absolute proper motions of 534 stars in the region of about 1° 5×1° 5 around the cluster M3 are determined. With the new data of proper motions, the membership probabilities of the stars are determined. The mean absolute proper motions for the cluster of -0 3±0 3 mas/yr in R.A. and -3 1±0 3 mas/yr in Dec. were obtained.Combining our results with the known distance and radial velocity of the cluster, we obtained its space motions and Galactic orbits in two different three component Galactic potentials.展开更多
成员判定是疏散星团研究中最关键的一步,成员判定的好坏直接影响对星团基本参数的估计.首次利用数据挖掘技术中的DBSCAN(Density-Based Spatial Clustering of Applications with Noise)聚类算法对疏散星团NGC 6791和M67(NGC 2682)分别...成员判定是疏散星团研究中最关键的一步,成员判定的好坏直接影响对星团基本参数的估计.首次利用数据挖掘技术中的DBSCAN(Density-Based Spatial Clustering of Applications with Noise)聚类算法对疏散星团NGC 6791和M67(NGC 2682)分别进行了成员判定,结果表明DBSCAN聚类算法能很有效地剔除场星污染.得到的NGC6791成员星的颜色-星等图上主序清晰并呈现明显的双重主序结构,这表明NGC 6791可能有更复杂的恒星形成与演化历史.对M67的分析表明出现了质量分层现象,并且星团的核心和外围两部分有明显的相对运动.对NGC 6791和M67的分析均表明DBSCAN聚类算法是一种有效的成员判定方法,有传统成员判定方法不具备的一些优点.展开更多
银河系光行差,或称为长期光行差漂移,是由于太阳系质心绕着银河系中心做轨道运动的加速度引起的视自行效应,量级大约为5μas·yr-1.在21世纪之前,由于观测精度尚未达到如此高的程度,人们很少讨论银河系光行差效应.随着甚长基线干涉(...银河系光行差,或称为长期光行差漂移,是由于太阳系质心绕着银河系中心做轨道运动的加速度引起的视自行效应,量级大约为5μas·yr-1.在21世纪之前,由于观测精度尚未达到如此高的程度,人们很少讨论银河系光行差效应.随着甚长基线干涉(Very Long Baseline Interferometer,VLBI)在基本天文学中的广泛应用和欧洲空间局(European Space Agency,ESA)的第2代微角秒天体测量卫星Gaia的问世,该效应显得逐渐重要.由于河外源的分布不均匀,银河系光行差效应会使得河外源天球参考架缓慢旋转,进而需要修正地球岁差参数,其中岁差速率的改正值大约为1μas·yr-1.对于微角秒精度的VLBI和Gaia参考架,银河系光行差将会引起框架扭曲,在两者的连接过程中,也是必须考虑的系统效应.展开更多
基金supported by grant No.BG051 PO001-3.3.06-0057 of the European Social Fund
文摘The proper motions of 15 nearby（d 〈 1 kpc） open clusters（OCs） were recalculated using data from the UCAC4 catalog. Only evolved or main sequence stars inside a certain radius from the center of the cluster were used. The results significantly differ from the ones presented by Dias et al.（2014）. This could be explained by a different approach in which we take the field star contamination into account. The present work aims to emphasize the importance of applying photometric criteria for the calculation of OC proper motions.
基金the National Science Foundation under Grant AST 09-37523T.C.B. acknowledges partial support for this work from grant PHY 08-22648Funding for the project has been provided by the National Development and Reform Commission
文摘We quantify and correct systematic errors in PPMXL proper motions using extragalactic sources from the first two LAMOST data releases and the Vbron-Cetty ＆ Vebron Catalog of Quasars. Although the majority of the sources are from the Veron catalog, LAMOST makes important contributions in regions that are not well-sampled by previous catalogs, particularly at low Galactic latitudes and in the south Galactic cap. We show that quasars in PPMXL have measurable and significant proper motions, which reflect the systematic zero-point offsets present in the catalog. We confirm the global proper motion shifts seen by Wu et al., and additionally find smaller-scale fluctuations of the QSO-derived corrections to an absolute frame. We average the proper motions of 158 106 extragalactic objects in bins of 3° ×3° and present a table of proper motion corrections.
文摘Analyzing Hipparcos proper motions of 1352 O B5 stars, we have found a clear stellar warping motion that is a systematic rotation +3 8±1 1 kms -1 kpc -1 of stars about the axis pointing to the galactic center in the sense of increasing the inclination of the HI warp, and a remarkably large galactic rotation of (V 0) O-B5 = 268 7 ± 11 9kms -1 , compared with the IAU recommendation (V 0 = 220 ± 20kms -1 ), given the galactocentric distance of the sun R 0 = 8 5kpc. Combining Hipparcos proper motions and the radial velocity data, we have then studied the kinematics for 151 classical cepheids. The results show a contracting motion of the Galaxy in the solar neibourhood, V θ/θ/R =-2 60 ± 1 07kms -1 kps -1 , which is along the solar circle. In the present paper, we have also analyzed proper motions of 21000 K-M giants, and again we found a large galactic rotation (V 0) K-M = 252 6±9 5kms -1 .
基金NKBRSF19990754 and National Natural Sciences Foundation under grant 19833010．
文摘We examine 14 plates of the globular cluster M3 (NGC 5272) taken with the 40 cm refractor at the Sheshan station of Shanghai Astronomical Observatory. The plates span over a period of about 77 years. The positions and absolute proper motions of eight stars in the Hipparcos Catalogue and of 49 stars in the Tycho-2 Catalogue are used as the reference frame. The astrometric reduction is made with the central overlapping principle. The absolute proper motions of 534 stars in a region of about 100' × 100' around the cluster are measured. With the new proper motion data the membership probabilities of the stars are determined. The average absolute proper motion obtained for the cluster is -0.06±0.30 mas yr-1 in R.A. and -2.6±0.30 mas yr-1 in Decl. By combining this result with the known distance and radial velocity of the cluster, we also obtained the Galactic orbit of M3 for a chosen three-component Galactic potential.
文摘We have obtained the absolute proper motion of globular cluster M3 from measurements of 14 plates taken with the 40cm refractor at Sheshan station of Shanghai observatory, spanning epoch is about 80 years. The positions and absolute proper motions of 24 stars in ACT catalogue are used as the reference frame. The reduction was made with the central overlapping principle. The absolute proper motions of 534 stars in the region of about 1° 5×1° 5 around the cluster M3 are determined. With the new data of proper motions, the membership probabilities of the stars are determined. The mean absolute proper motions for the cluster of -0 3±0 3 mas/yr in R.A. and -3 1±0 3 mas/yr in Dec. were obtained.Combining our results with the known distance and radial velocity of the cluster, we obtained its space motions and Galactic orbits in two different three component Galactic potentials.
文摘银河系光行差,或称为长期光行差漂移,是由于太阳系质心绕着银河系中心做轨道运动的加速度引起的视自行效应,量级大约为5μas·yr-1.在21世纪之前,由于观测精度尚未达到如此高的程度,人们很少讨论银河系光行差效应.随着甚长基线干涉(Very Long Baseline Interferometer,VLBI)在基本天文学中的广泛应用和欧洲空间局(European Space Agency,ESA)的第2代微角秒天体测量卫星Gaia的问世,该效应显得逐渐重要.由于河外源的分布不均匀,银河系光行差效应会使得河外源天球参考架缓慢旋转,进而需要修正地球岁差参数,其中岁差速率的改正值大约为1μas·yr-1.对于微角秒精度的VLBI和Gaia参考架,银河系光行差将会引起框架扭曲,在两者的连接过程中,也是必须考虑的系统效应.
