New proper motions have been derived from reductions of PDS microdensitometer scans of 17 Yerkes refractor plates spanning an epoch range of 88 years for 515 stars down to V~15.6 in the region of the globular cluster M5. Photographic photometry in B and V has been obtained for these stars from these scans and scans of six Yerkes reflector plates. The present proper motions have significantly improved precision compared to Cudworth [AJ, 84, 1866 (1979)]. Membership probabilities derived from the new proper motions are largely in agreement with those from Cudworth's study, but this paper includes nearly 200 additional stars, many of which are probable members. A color-magnitude diagram of probable members is presented and discussed, as well as comparisons to previous photometry. All but two of the previously known or suspected variables are found to be highly probable members. These proper motions have been used by Cudworth & Hanson [AJ, 105, 168 (1993)] to derive a large space velocity for M5, implying that it is a rich outer halo cluster on an eccentric orbit near perigalacticon. These motions will be used in a forthcoming paper to explore the internal dynamics of M5, including a derivation of the cluster distance by comparison of the proper motion and radial velocity dispersions.
We present the results of an internal proper motion analysis of the inner region of M15 using Hubble Space Telescope Wide Field Planetary Camera 2 images. The motions of 704 stars with brightnesses above that of the cluster turnoff (V<18.3) are analyzed to determine the velocity dispersion profile within about 15" of the cluster center. The average signal-to-noise ratio of these motions is about 3, and stars in the innermost radial bin have an average core distance of only 0.7". Assuming a distance to M15 of 10kpc, we estimate that the velocity dispersion within this innermost bin is 14.5+/-2.5km/s and that it slowly decreases outward, reaching a value of 9.8+/-0.8km/s at R=15.6". We find that the proper-motion dispersion profile is in good agreement with the predictions of recent N-body simulations that do not require the presence of a central intermediate-mass black hole (IMBH). The agreement between the observed profile and the N-body simulations is marginally improved if one assumes that when a neutron star is created as a result of stellar evolution, it escapes from the cluster. Based on the results of this study and a review of other investigations, it is concluded that there is little direct evidence that M15 possesses an intermediate-mass black hole.
Relative proper motions of 872 stars in the open cluster M 11 region are reduced using 10 plate pairs taken over time baselines of 16~70 years with the double astrograph telescope of Shanghai Observatory. The scale is 30"/mm. The plates were measured with the PDS machines in the Purple Mountain Observatory in Nanjing and the Institute of Technology and Communication in Luoyang, China. The average proper motion accuracy is about 1.1mas/yr with 85% of the data better than 1mas/yr. Membership probabilities of 785 stars within 25' centred on M 11 are determined based on their proper motions. The method used is suggested by Su et al. (1995AcApS..15..217S) with some improvements of Zhao & He (1990A&A...237...54Z), in which the space distribution and magnitude dependencies for cluster stars are taken into account. The results are significantly good. The total integrated membership probabilities for all these stars is 547 and the number of stars with probabilities higher than 0.7 is 541. It can be found after the membership determination that there exists mass segregation in M 11. Some comparisons and discussion are also given.
Relative proper motions and membership probabilities of 1046 stars in the open cluster M67 are are determined from PDS measurements of 9 plate pairs taken with the double astrograph at the Zo-Se station Shanghai Observatory, which has an aperture of 40cm, a focal length of 6.9m and a scale of 30"/mm. The number of stars with membership probabilities higher than 0.8 and at a distance less than 45' from the field center is 282. The average standard errors of proper motions vary from +/-0.0004"/yr for bright stars in the inner part of the field to some +/-0.0015"/yr for faint stars in the outer part of the cluster. It is shown by a detailed discussion that the proper motions and membership probabilities of the stars determined in this paper are in quite satisfactory agreement wit those obtained by Sanders (1977A&AS...27...89S) or Girard et al. (1989AJ.....98..227G).
The results of the Koenigstuhl survey in the Southern Hemisphere are presented. I have searched for common proper motion companions to 173 field very low mass stars and brown dwarfs with spectral types >M5.0 V and magnitudes J<~14.5mag. I have measured for the first time the common proper motion of two new wide systems containing very low mass components, Koenigstuhl 2 AB and 3 A-BC. Together with Koenigstuhl 1 AB and 2M 0126-50 AB, they are among the widest systems in their respective classes (r=450-11900AU). I have determined the minimum frequency of field wide multiples (r>100AU) with late-type components at 5.0%+/-1.8% and the frequency of field wide late-type binaries with mass ratios q>0.5 at 1.2%+/-0.9%. These values represent a key diagnostic of evolution history and low-mass star and brown dwarf formation scenarios. In addition, the proper motions of 62 field very low mass dwarfs are measured here for the first time.
This catalogue was prepared during the study of proper motions (Platais 1991A&AS...87...69P) in and around the open cluster NGC 752 (C0154+374) which belongs to the poorly-populated open cluster class. Relative proper motions of 1777 stars have been determined from the PDS measurements of 11 Pulkovo normal astrograph plates (scale is 59.57"/mm) in a 110'-diameter circle around the cluster. The catalogue of proper motions is complete down to mpg=15.0m, the limiting value is 15.4m. The average standard error of the catalogue proper motions varies from 0.75mas/yr (milliarcseconds per year) for stars with mpg<14.0m to 1.1mas/yr for the rest. These errors refer to the highest weight group (the star is present on all or nearly all plate pairs). In order to calculate the standard error of a star belonging to the lower weight group, it is necessary to use a unit weight error of 3.7 mas/yr and the appropriate weights from Table I for the plate pairs used in the determination of the star's proper motion, as given in the Catalogue. For stars located far from the field centre as well for fainter stars, an additional factor proportional to the accuracy degradation should be applied. Table I. Assigned weights. ------------------------------------------------------------------- | Pair No.| 1 | 2 | 3 | 4 | 5 | 6 | 7 | |---------|-------|-------|-------|-------|-------|-------|-------| | Weight | 7.0 | 7.0 | 2.5 | 2.3 | 2.8 | 3.0 | 1.0 | ------------------------------------------------------------------- Example: For the star No. 40 the weighted standard error of the proper motion is as follows: 3.7/sqrt(2.3+2.8)*1.5=2.5 mas/yr. The degradation factor of 1.5 comes from the decreased accuracy for the faint stars located at the edge of the field investigated. More detailed information on measured plates, standard errors, assigned weights, membership probabilities etc. is given in Platais (1991A&AS...87...69P). The membership probabilities were calculated assuming that on the vector-point diagram the distribution of field stars is essentially flat within a limited area around the centroid of the cluster member proper motion distribution. A clear separation of field and cluster stars is achieved.
The astrometric accuracy of triple image Carte du Ciel plates has been analysed using plates of the open cluster NGC 1647. A new multithreshold technique was used for the treatment of the triple image plates. Accuracies ranging from 100mas to 200mas were found. We determined proper motions with a median accuracy of 1.6mas/a for 2220 stars in the field of NGC 1647. The membership probabilities of stars in the cluster region agree very well with the data of Francic (1989). Due to a significant difference of the proper motions of SZ Tau and the cluster members, SZ Tau seems not to be a member of NGC 1647.
From photographic plate data of Shanghai Astronomical Observatory with a time baseline of 87 years, proper motions and membership probabilities of 364 stars in the open cluster NGC 6530 region are reduced. On the basis of membership determination, luminosity function and segregation effect of the cluster are discussed with details. Spatial mass segregation is obviously present in NGC 6530 while there is no clear evidence for a velocity-mass (or velocity-luminosity) dependence. The observed spatial mass segregation for NGC 6530 might be due to a combination of initial conditions and relaxation process.
The results of astrometric and photometric investigations of the open cluster NGC 7243 are presented. Proper motions of 2165 stars with root-mean-square error of 1.1mas/yr were obtained by means of PDS scanning of astrometric plates covering the time interval of 97 years. A total of 211 cluster members down to V=15.5mag have been identified. V and B magnitudes have been determined for 2118 and 2110 stars respectively. Estimations of mass 348M_{sun}_<M<522M_{sun}_, age t=2.510^8^yr, distance r=698pc and reddening E(B-V)=0.24 of the cluster NGC 7243 have been made.
