The combination of precise radial velocities from multi-object spectroscopy and highly accurate proper motions from Gaia DR2 opens up the possibility for detailed 3D kinematic studies of young star-forming regions and clusters. Here, we perform such an analysis by combining Gaia-ESO Survey spectroscopy with Gaia astrometry for ~900 members of the Lagoon Nebula cluster, NGC 6530. We measure the 3D velocity dispersion of the region to be 5.35^+0.39^_-0.34_km/s, which is large enough to suggest the region is gravitationally unbound. The velocity ellipsoid is anisotropic, implying that the region is not sufficiently dynamically evolved to achieve isotropy, though the central part of NGC 6530 does exhibit velocity isotropy that suggests sufficient mixing has occurred in this denser part. We find strong evidence that the stellar population is expanding, though this is preferentially occurring in the declination direction and there is very little evidence for expansion in the right ascension direction. This argues against a simple radial expansion pattern, as predicted by models of residual gas expulsion. We discuss these findings in the context of cluster formation, evolution, and disruption theories.
We measure the mean halo mass of z=~0.5 MgII absorbers using the cross-correlation (over comoving scales 0.05-13h^-1^Mpc) between 1806 MgII quasar absorption systems and ~250000 luminous red galaxies (LRGs), both selected from the Sloan Digital Sky Survey Data Release 3.
The published report was prepared by R.T. Hall (1974) for the Space and Missile systems Organization, Air Force System Command. The machine version includes a 10-micrometer catalog number, object name, right ascension and declination (B1950), galactic coordinates, proper motions, spectral types, magnitudes in the V(0.55um), I(0.84um), K(2.2um) and N(10um) bands, flux measurements at 10um, and cross identifications to the numbering systems of the Durchmusterung catalogs, the SAO catalog, the Bright Star Catalogue, The Henry Draper Catalogue and the GC, and CalTech Two-Micron Sky Survey (Neugebauer and Leighton, Cat. II/2) where such identifications exist.
The catalogue of equivalent widths (EW) for neutral helium lines presented is based on numerous photographic spectral observations of B-stars made during 1978-1986 with the 6m telescope of Special Astrophysical Observatory of Russian Academy of Sciences. Original results of spectroscopy of B-stars inside the galactic open clusters and stellar associations were published by Klochkova and Panchuk in 1986PAZh...12..928K and 1987PAZh...13...56K. To make easier the procedure of EW reduction, several A- and O-stars were included in the Catalogue. All sequent steps of EW reduction were described in Klochkova and Panchuk (1987SoSAO..54....5K, Neutral Helium Lines in the Spectra of B-Stars - Part One - Catalogue). Due to profiles of HeI lines are essentially distinguished in spectra both of supergiants and normal stars, the procedure of EW reduction were made separately for these types of stars. After reduction to the common system of the published data and of observational data obtained by authors a homogeneous catalogue of equivalent widths EW for eight neutral helium lines (HeI, {lambda} 4009, 4026, 4121, 4144, 4387, 4471, 4713{AA}) for 524 stars is compiled. The catalogue is added by the mean values of EW for H{gamma} and H{delta} lines being also reduced to the common system of equivalent widths. The work is supported by the Russian Fondation for Basic Research (project 05-07-90087).
An atlas of 90 northern dwarf novae (delta greater than 20{deg}) is presented. It is meant to supplement the Atlas of Southern and Equatorial Dwarf Novae of Vogt and Bateson (1982). Together, these publications represent a comprehensive collection of dwarf nova finding charts for the whole sky. In addition to the atlas, coordinates are given for most of the dwarf novae with accuracies significantly higher than published hitherto.
OB associations are unbound groups of young stars made prominent by their bright OB members, and have long been thought to be the expanded remnants of dense star clusters. They have been important in astrophysics for over a century thanks to their luminous massive stars, though their low-mass members have not been well studied until the last couple of decades. This has changed thanks to data from X-ray observations, spectroscopic surveys and astrometry from Gaia that allows their full stellar content to be identified and their dynamics to be studied, which in turn is leading to changes in our understanding of these systems and their origins, with the old picture of Blaauw (1964a) now being superseded. It is clear now that OB associations have considerably more substructure than once envisioned, both spatially, kinematically and temporally. These changes have implications for the star formation process, the formation and evolution of planetary systems, and the build-up of stellar populations across galaxies.
The ephemeris of Phoebe, the ninth satellite of Saturn, is not very accurate. Previous dynamical models were usually too simplified, the astrometry is heterogeneous and, the Saturn's ephemeris itself is an additionnal source of error. The aim is to improve Phoebe's ephemeris by using a large set of observations, correcting some systematic errors and updating the dynamical model.
The catalogue is a result of studies of wide neighborhoods of 513 open clusters and 7 compact associations carried out in high precision homogeneous all sky catalogue ASCC-2.5 (Kharchenko, 2001, Cat. <I/280>). On the basis of data on about 33000 possible members (including about 10000 most probable ones) and homogeneous methods of cluster parameter determination the angular sizes of cluster cores and coronae, cluster heliocentric distances, mean proper motions, mean radial velocities and ages were established and collected in the COCD. These include cluster distances for 200 clusters, average cluster radial velocities for 94 clusters, and cluster ages for 195 clusters derived for the first time. Clusters in the catalogue are sorted by right ascension J2000 order. The Open Cluster Diagrams Atlas (OCDA) presents a set of open cluster diagrams used for the determination of parameters of 513 open clusters and 7 compact associations, and is intended to illustrate the quality of the constructed cluster membership (Kharchenko et al., 2004, Cat. <J/AN/425/740>), and the accuracy of the derived cluster parameters (this paper). Every diagram presents relation between various stellar data from all sky catalogue ASCC-2.5 (Kharchenko 2001, Cat. <I/280>) in area of the specific cluster. There are five diagrams provided for every cluster in the Atlas: the area map, the density profile, the vector point diagram, the magnitude equation diagram, and the color-magnitude diagram. The OCDA consists of 520 PostScript plots stored as gzipped files (i.e. one file per cluster).
Catalogue of open cluster parameters from UBV-data.
Short Name:
V/96
Date:
21 Oct 2021
Publisher:
CDS
Description:
The authors constructed the homogeneous set of galactic open cluster parameters (reddenings, distances, ages and partly metallicities) using published UBV-photometry data (Loktin, Matkin, 1992). The catalogue contains data on 340 clusters.
