scholarly journals 8. Commission de l’Astronomie Méridienne

1933 ◽  
Vol 4 ◽  
pp. 28-31
Author(s):  
Frank Dyson ◽  
MM. Aiginitis ◽  
Armellini ◽  
Bemporad ◽  
Boss ◽  
...  
Keyword(s):  
Milky Way ◽  
Systematic Errors ◽  
Special Importance ◽  
Proper Motions ◽  
International Astronomical Union ◽  
Systematic Correction ◽  
International Astronomical ◽  
Right Ascension

Since the last meeting of the International Astronomical Union, much attention has been given both in Germany and America to the systematic errors of the fundamental catalogues of Boss and Auwers. This is of special importance if the proper motions of any of the stars are to be used in the verification of the rotation in the plane of the Milky Way. The periodic errors in the proper motions, both in right ascension and declination, are of significance in this connection, while the motion of the equinox is required for the determination of precession, and the systematic correction to the proper motions of declination affects the position of the Solar Apex and the Vertices of the Star Streams.

scholarly journals Commission 24. (Stellar Parallaxes and Proper Motions.)

1933 ◽  
Vol 4 ◽  
pp. 246-247
Author(s):  
S. A. Mitchell ◽  
F. Slocum
Keyword(s):  
Systematic Errors ◽  
Proper Motions ◽  
Fundamental Assumption ◽  
Trigonometric Parallaxes ◽  
Informal Discussion ◽  
Right Ascension

There were two meetings of the Commission. The first meeting was devoted to an informal discussion of programmes for parallax work. The second session was devoted to a discussion of systematic errors. The President gave a brief summary of the two latest determinations of the systematic errors of trigonometric parallaxes, by Schlesinger (parallaxes published to 1924) and by van Maanen (parallaxes to 1927). Both investigators had used the same basis of comparison, namely, the Mt Wilson spectroscopic parallaxes, and both had made the same fundamental assumption, namely, that the systematic errors of the spectroscopic parallaxes depending on right ascension were negligible.

scholarly journals A Determination of Secular Parallaxes of Reference Stars from Relative Proper Motions of Open Clusters

1970 ◽  
Vol 7 ◽  
pp. 74-76
Author(s):  
A. N. Deutsch
Keyword(s):  
Systematic Errors ◽  
Open Clusters ◽  
Radial Velocities ◽  
Proper Motions ◽  
The Mean

The determination of secular parallaxes of stars is usually based on meridian observations of proper motions of bright stars, this introducing known systematic errors. The mean parallaxes of stars can be obtained by means of radial velocities which are known for the bright stars. The more perspective method, the reference of stars to galaxies, is not applicable at low galactic latitudes.

scholarly journals A New Absolute Proper Motion Determination of Leo I Using HST/WFPC2 Images and Gaia EDR3

2021 ◽  
Vol 163 (1) ◽  
pp. 1
Author(s):  
Dana I. Casetti-Dinescu ◽  
Caitlin K. Hansen ◽  
Terrence M. Girard ◽  
Vera Kozhurina-Platais ◽  
Imants Platais ◽  
...  
Keyword(s):  
Proper Motion ◽  
Milky Way ◽  
Proper Motions ◽  
Large Area ◽  
Field Of Study ◽  
Data Set ◽  
Polar Structure ◽  
The Galaxy ◽  
The Absolute

Abstract We measure the absolute proper motion of Leo I using a WFPC2/HST data set that spans up to 10 yr to date the longest time baseline utilized for this satellite. The measurement relies on ∼2300 Leo I stars located near the center of light of the galaxy; the correction to absolute proper motion is based on 174 Gaia EDR3 stars and 10 galaxies. Having generated highly precise, relative proper motions for all Gaia EDR3 stars in our WFPC2 field of study, our correction to the absolute EDR3 system does not rely on these Gaia stars being Leo I members. This new determination also benefits from a recently improved astrometric calibration of WFPC2. The resulting proper-motion value, (μ α , μ δ ) = (−0.007 ± 0.035, − 0.119 ± 0.026) mas yr−1 is in agreement with recent, large-area, Gaia EDR3-based determinations. We discuss all the recent measurements of Leo I’s proper motion and adopt a combined, multistudy average of ( μ α 3 meas , μ δ 3 meas ) = ( − 0.036 ± 0.016 , − 0.130 ± 0.010 ) mas yr−1. This value of absolute proper motion for Leo I indicates its orbital pole is well aligned with that of the vast polar structure, defined by the majority of the brightest dwarf spheroidal satellites of the Milky Way.

scholarly journals Using Gaia for studying Milky Way star clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 536-539
Author(s):  
Eugene Vasiliev
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Velocity Dispersion ◽  
Systematic Errors ◽  
Space Distribution ◽  
Proper Motions ◽  
Integrals Of Motion ◽  
Spatially Correlated ◽  
Dimensional Phase Space ◽  
Best Fit

AbstractWe review the implications of the Gaia Data Release 2 catalogue for studying the dynamics of Milky Way globular clusters, focusing on two separate topics.The first one is the analysis of the full 6-dimensional phase-space distribution of the entire population of Milky Way globular clusters: their mean proper motions (PM) can be measured with an exquisite precision (down to 0.05 mas yr−1, including systematic errors). Using these data, and a suitable ansatz for the steady-state distribution function (DF) of the cluster population, we then determine simultaneously the best-fit parameters of this DF and the total Milky Way potential. We also discuss possible correlated structures in the space of integrals of motion.The second topic addresses the internal dynamics of a few dozen of the closest and richest globular clusters, again using the Gaia PM to measure the velocity dispersion and internal rotation, with a proper treatment of spatially correlated systematic errors. Clear rotation signatures are detected in 10 clusters, and a few more show weaker signatures at a level ∼0.05 mas yr−1. PM dispersion profiles can be reliably measured down to 0.1 mas yr−1, and agree well with the line-of-sight velocity dispersion profiles from the literature.

scholarly journals Absolute Proper and Space Motion of the Globular Cluster M2

1994 ◽  
Vol 161 ◽  
pp. 464-466
Author(s):  
M. Geffert ◽  
C. Forner ◽  
M. Hiesgen ◽  
A.R. Klemola
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Reference Frames ◽  
Proper Motions ◽  
The Past ◽  
Motion Study ◽  
Space Motion ◽  
First Results

Space motions of globular clusters are important for the understanding of the kinematics and chemical evolution of the Milky Way. The greatest problem for the determination of the space motions of the globular clusters arises from the difficulties of getting absolute proper motions. In the past these were determined using classical stellar reference frames, modelling of the non-cluster stars in the field and extragalactic objects in the region of the cluster (see e.g. Cudworth & Hanson 1993; Geffert et al. 1993 for references). However, as shown for M 15 and M 3 (Geffert et al. 1993; Tucholke et al. 1993), the results based on different methods for deriving the absolute proper motions differ by up to yrs. In order to get a more complete view of the differences between the various methods it is therefore very interesting to get absolute proper motions based on all three methods for further objects. We present here the first results of a new proper motion study of the globular cluster M 2.

scholarly journals J2000.0

1986 ◽  
Vol 7 ◽  
pp. 73-76
Author(s):  
Clayton Smith
Keyword(s):  
Reference Frame ◽  
Proper Motions ◽  
International Astronomical Union ◽  
International Astronomical ◽  
Number Of Authors

It was recommended in a resolution of the International Astronomical Union that as of Jan. 1, 1984, a new astronomical reference frame would be adopted (IAU 1976). This reference frame has been designated as the FK5 reference frame of J2000.0. The problem of the interim realization of this reference frame pending completion of work on the compilation of the FK5 catalog at the Astronomisches Rechen-institut has been addressed by a number of authors, see, e.g., Kaplan(1981), Standish(1983), Aoki et al.(1983), and Lederle and Schwan(1984). Their discussions are primarily concerned with the steps which must be taken to transform FK4 catalog positions and proper motions referred to the equator, equinox and epoch of B1950.0 to J2000.0. The primary emphasis of the following discussion is on the transformation of catalogs other than the FK4 to the J2000.0 equinox. There are a few remarks concerning the FK4 catalog.

scholarly journals 30. Commission des Vitesses Radiales Stellaires

1933 ◽  
Vol 4 ◽  
pp. 178-189
Author(s):  
M. J. S. Plaskett ◽  
MM. Adams ◽  
W. W. Campbell ◽  
Frost ◽  
Hamy ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Radial Velocities ◽  
University Of Michigan ◽  
International Astronomical Union ◽  
Short Summary ◽  
International Astronomical ◽  
Ann Arbor ◽  
The University

The four years that have elapsed since the last meeting of the International Astronomical Union have witnessed steady progress in the determination of radial velocities, principally at the Mt Wilson Observatory, Pasadena, Cal., the Lick Observatory, Mt Hamilton, Cal., the Yerkes Observatory, Williams Bay, Wis., the Dominion Astrophysical Observatory, Victoria, B.C., the Observatory of the University of Michigan, Ann Arbor, Mich., and the Simeis Observatory in Russia. It will be useful, for the members of the Commission, to give a short summary of the radial velocity work completed and in progress since the last meeting.

scholarly journals Maintenance and densification: current proper-motion catalogs

2007 ◽  
Vol 3 (S248) ◽  
pp. 303-309
Author(s):  
T. M. Girard
Keyword(s):  
Proper Motion ◽  
Reference System ◽  
Milky Way ◽  
Raw Material ◽  
Proper Motions ◽  
Schmidt Telescope ◽  
Large Area ◽  
Milky Way Galaxy ◽  
Celestial Reference System

AbstractAn overview of currently available, large-area, proper-motion catalogs is presented. These include the well-known catalogs based on historical Schmidt-telescope surveys as well as other projects that make use of observational material the primary purpose of which, from inception, was the determination of proper motions. The various catalogs are characterized and compared, with an emphasis on their limitations and their appropriateness for various astrophysical uses.In addition to allowing for the maintenance of a practical celestial reference system, absolute proper-motion surveys provide the raw material from which a better understanding of our Galaxy's structure and kinematics can be built. Several examples will be cited in which large proper-motion surveys are used to probe and describe the distinct stellar components that comprise our Milky Way Galaxy.

scholarly journals 24. Commission des Parallaxes Stellaires et des Mouvements Propres

1936 ◽  
Vol 5 ◽  
pp. 144-155
Author(s):  
M. S. A. Mitchell ◽  
MM. Adams ◽  
Alden ◽  
Bianchi ◽  
Cecchini ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Systematic Errors ◽  
Probable Error ◽  
Proper Motions ◽  
Astrophysical Journal ◽  
Trigonometric Parallaxes ◽  
Substantial Progress

In November 1934 the President circulated a letter to the members of the Commission as follows:Since the 1932 meeting the following projects have been completed, or are nearing completion:(1)The publication of many lists of trigonometric parallaxes.(2)The determination of the spectroscopic parallaxes of 4179 stars at Mt Wilson Observatory by Adams, Joy and Humason.(3)A discussion of systematic errors of trigonometric parallaxes by van Maanen and a re-discussion in the Astrophysical Journal of the same material by Mitchell and by Sterne.(4)The compilation of a second Yale Catalogue to include parallaxes completed before the end of 1934.(5)Substantial progress on the proper motions of 32,000 stars by Boss and his associates at the Dudley Observatory.(6)The publication at the Radcliffe Observatory of the proper motions of 32,000 stars from photographs on 115 Selected Areas.(7)The completion of the dynamical parallaxes of 2000 stars.(8)The completion of the proper motions of 18,000 stars derived from parallax plates at the Leander McCormick Observatory.(9)The publication at the Yale Observatory of the proper motions of 40,000 stars with a probable error less than 0”.010 determined from photographs by re-observing in zones the Astronomische Gesellschaft stars.(10)The determination of the proper motions of 50,000 stars in the Southern Hemisphere by Luyten from Harvard photographs.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

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