3D cluster members and near-infrared distance of open cluster NGC 6819

作     者：Xin-Hua Gao Shou-Kun Xu Li Chen 

作者机构：School of Information Science and EngineeringChangzhou University Shanghai Astronomical ObservatoryChinese Academy of Sciences 

出 版 物：《Research in Astronomy and Astrophysics》 (天文和天体物理学研究（英文版）)

年 卷 期：2015年第15卷第12期

页      面：2193-2203页

核心收录：

学科分类：07[理学] 070401[理学-天体物理] 0704[理学-天文学] 

基　　金：supported by the National Natural Science Foundation of China(NSFC Grant No.11403004) the School Foundation of Changzhou University(ZMF1002121) support by the 973 Program(2014 CB845702) the Strategic Priority Research Program"The Emergence of Cosmological Structures"of the Chinese Academy of Sciences(CAS grant XDB09010100) the NSFC(Grant No.11373054) 

主　　题：open clusters and associations: individual (NGC 6819)    Hertzsprung Russell and C M diagrams    stars: kinematics and dynamics    stars: distances 

摘      要：In order to obtain clean members of the open cluster NGC 6819, the proper motions and radial velocities of 1691 stars are used to construct a three-dimensional （3D） velocity space. Based on the DBSCAN clustering algorithm, 537 3D cluster members are obtained. From the 537 3D cluster members, the average radial velocity and absolute proper motion of the cluster are Vr = ＋2.30 ±0.04 km s-1 and （PMRA, PMDec） = （-2.5 ±0.5, -4.3 ± 0.5） mas yr-1, respectively. The proper motions, radial velocities, spatial positions and color-magnitude diagram of the 537 3D members indicate that our membership determination is effective. Among the 537 3D cluster members, 15 red clump giants can be easily identified by eye and are used as reliable standard candles for the distance estimate of the cluster. The distance modulus of the cluster is determined to be （m - M）0 -- 11.86 ± 0.05 mag （2355 ±54 pc）, which is quite consistent with published values. The uncertainty of our distance mod- ulus is dominated by the intrinsic dispersion in the luminosities of red clump giants （--0.04 mag）.