We have used COSMOS scans of photographic plates taken by the Palomar Oschin Schmidt telescope (as part of the original Palomar Sky Survey) and by the UK Schmidt telescope to obtain proper motions for ~ 450 000 stars within a 112-degree region covering part of the Hyades cluster. With epoch differences of 33 to 37 yr, we have obtained proper motions accurate to 6-12 mas/yr and have identified 393 candidate Hyads to a limiting magnitude of Mv ~ +15.5, including at least two new white dwarf candidates. The main-sequence luminosity function determined from our sample is similar to that defined by local field stars, with a broad maximum at Mv ~ +12. Deriving distances from mu u, the proper motion towards the convergent point, and the space velocity determined by Gunn et al., we find stars with motions consistent with membership at distances of more than 15pc from the cluster centre. Moreover, both the line-of-sight and surface density distributions show evidence for significant mass segregation - indeed, the overall proper motion distribution suggests a tight core centred within a much broader distribution. We derive a total mass of 410-480Sun and a gravitational binding radius of ~ 10.5pc.
The proper motion measurements for 142 previously known L and T dwarfs are presented. From this sample we identify and discuss eight high-velocity L dwarfs. We also find four new wide common proper motion binaries/multiple systems. Using the moving cluster methods we have also identified a number of L dwarfs that may be members of the Ursa Major (age~400Myr), the Hyades (age~625Myr) and the Pleiades (age~125Myr) moving groups.
By using images taken with Wide Field Camera (WFCAM) on United Kingdom Infrared Telescope (UKIRT) and Son of ISAAC (SofI) on the New Technology Telescope (NTT) and combining them with Two Micron All Sky Survey (2MASS) we have measured proper motions for 125 L and T dwarfs in the dwarf archive. Two of these L dwarfs appear to have M dwarf common proper motion companions, and two also appear to be high-velocity dwarfs, indicating possible membership of the thick disc. We have also compared the motion of these 125 objects to that of numerous moving groups, and have identified new members of the Hyades, Ursa Major and Pleiades moving groups. These new objects, as well as those identified in Jameson et al. have allowed us to refine the L dwarf sequence for Ursa Major that was defined by Jameson et al, 2008 (Cat. J/MNRAS/384/1399).
Large-scale astrometric and photometric data bases have been used to search for and confirm stellar membership of the open cluster IC 2391. 125 stars were found that satisfied criteria for membership based on proper motion components and BRI photometry from the United States Naval Observatory B (USNO-B, Cat. <I/284>) catalogue and JHK photometry from the Two Micron All Sky Survey (2MASS, Cat. <II/246>) catalogue. This listing was compared with others recently published. A distance to the cluster of 147.7+/-5.5pc was found with mean proper motion components, from the Tycho2 catalogue of (-25.04+/-1.53mas/yr; +23.19+/-1.23mas/yr). A revised Trumpler classification of II3r is suggested. Luminosity and mass functions for the candidate stars were constructed and compared with those of field stars and other clusters.
The wide neighborhoods of 401 open clusters are analysed using the the modern, high precision, homogeneous all sky ASCC-2.5 all-sky catalogue (Kharchenko, 2001, Cat. <I/280>). More than 28000 possible members (including about 12500 most probable ones) are identified using kinematic and photometric criteria. Star counts with the ASCC-2.5 and USNO-A2.0 (Cat. <I/252>) catalogs are used to determine the angular and linear radii of cluster cores and coronae, which exceed the previous published values by factors of two or three. The mean proper motions are determined directly in the Hipparcos system for 401 open clusters, for 183 of them for the first time. The heliocentric distances of 118 clusters are determined for the first time based on color-magnitude diagrams for the identified members.
We present a catalog of mean proper motions and membership probabilities of individual stars for optically visible open clusters, which have been determined using data from the UCAC4 catalog in a homogeneous way. The mean proper motion of the cluster and the membership probabilities of the stars in the region of each cluster were determined by applying the statistical method in a modified fashion. In this study, we applied a global optimization procedure to fit the observed distribution of proper motions with two overlapping normal bivariate frequency functions, which also take the individual proper motion errors into account. For 724 clusters, this is the first determination of proper motion, and for the whole sample, we present results with a much larger number of identified astrometric member stars. Furthermore, it was possible to estimate the mean radial velocity of 364 clusters (102 unpublished so far) with the stellar membership using published radial velocity catalogs. These results provide an increase of 30% and 19% in the sample of open clusters with a determined mean absolute proper motion and mean radial velocity, respectively.
The mean proper motions of 390 galactic open clusters with radial-velocity measurements are computed from the data of the Tycho-2 catalog (<I/259>) using the kinematic and photometric cluster membership criteria.
We present lists of proper-motions and kinematic membership probabilities in the region of 49 open clusters or possible open clusters. The stellar proper motions were taken from the Bordeaux PM2000 catalogue. The segregation between cluster and field stars and the assignment of membership probabilities was accomplished by applying a fully automated method based on parametrisations for the probability distribution functions and genetic algorithm optimisation heuristics associated with a derivative-based hill climbing algorithm for the likelihood optimization.
Relative proper motions, their corresponding observed errors and membership probabilities of 2400 stars in the open cluster NGC 2286 region are determined from ASTROSCAN measurements of 8 plates made at Leiden Observatory. The plates have the maximum epoch difference of some 70 years and were taken with the double astrograph at Zo-Se station of Shanghai Observatory, which has an aperture of 40 cm, a focal length of 6.9 m and a scale of 30 arcsec/mm. The number of stars with membership probabilities higher than 0.7 and radial distances from the cluster centre less than 12' is 90. The average standard errors of proper motions vary from +/-0.0007"/yr for bright stars in the inner part of the field to some +/-0.0016"/yr for faint stars in the outer part of the field, and are statistically dependent on the number of measured plates per star. It is found from an analysis of the surface number density distribution of cluster members that the angular radius of NGC 2286 is some 12' and the corresponding linear radius 4.5 pc.
