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 Proper Motions of OB Stars in Both Hemispheres

1974 ◽  
Vol 61 ◽  
pp. 227-227
Author(s):  
Haruo Yasuda
Keyword(s):  
Southern Hemisphere ◽  
Fundamental System ◽  
Systematic Errors ◽  
Radial Velocities ◽  
Distance Scale ◽  
Proper Motions ◽  
Stellar Kinematics ◽  
Ob Stars

From a comparison between the rotational velocities derived from radial velocities and space motions of OB stars, large systematic errors of FK4 proper motions in the southern hemisphere are evaluated; these may be expected, from the known accuracy of the FK4. The error of adopted distance scale is also examined. It is suggested that meridian observations of OB stars should be extended to the southern hemisphere to further researches, not only on stellar kinematics, but also on the fundamental system.

The determination of the cross sections for the reactions 27 Al( n , α ) and 56 Fe( n , p ) for 14 MeV neutrons by an absolute method

1966 ◽  
Vol 292 (1429) ◽  
pp. 180-192 ◽  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Standard Error ◽  
Particle Method ◽  
Systematic Errors ◽  
Aluminium Foil ◽  
The Mean ◽  
The Cross ◽  
Experimental Values

Measurements of the cross sections for the reactions 27 Al( n , α ) 24 Na and 56 Fe( n, p ) 56 Mn for neutrons of energy 13.5 ± 0.1 MeV have been made by a radioactivation method. The neutron flux was determined by a variant of the 'associated particle’ method, in which the α -particles produced concurrently with the neutrons from the D + T reaction were estimated in terms of the volume of helium which accumulated when they were brought to rest in an aluminium foil. Cross section values obtained at 13.5 MeV were: for 27 Al( n , α ): 118.1 ± 6.0 mb : for 56 Fe( n, p ): 106.7 ± 4.7 mb. The errors quoted include both the standard error on the mean of the experimental values and an estimate of possible residual systematic errors. The excitation functions for both reactions in the energy region 13.5 to 14.8 MeV have also been investigated, in order to provide secondary cross section values over this range of energies. At 14.8 MeV the values found were: 27 Al( n , α )103.6 ± 5.5 mb; 56 Fe( n, p )96.7 ± 4.5 mb.

scholarly journals Stellar Spins in the Pleiades, Praesepe, and M35 Open Clusters

2021 ◽  
Vol 923 (1) ◽  
pp. 23
Author(s):  
Brian F. Healy ◽  
P. R. McCullough ◽  
Kevin C. Schlaufman
Keyword(s):  
Systematic Error ◽  
Open Clusters ◽  
Photometric Data ◽  
Radial Velocities ◽  
Proper Motions ◽  
Kinematics Analysis ◽  
Mean Velocity ◽  
Clockwise Direction ◽  
Single Cluster

Abstract We analyze spectroscopic and photometric data to determine the projected inclinations of stars in three open clusters: the Pleiades, Praesepe, and M35. We determine the sin i values of 42, 35, and 67 stars in each cluster, respectively, and from their distributions we find that isotropic spins and moderate alignment are both consistent with the Pleiades and Praesepe data. While it is difficult to distinguish between these scenarios for a single cluster, an ensemble of such distributions may facilitate a distinction. The M35 inclination distribution is most consistent with a superposition of isotropic and anisotropic spins, the source of which could be systematic error or a physical grouping of aligned stars. We also study internal cluster kinematics using radial velocities and proper motions. Our kinematics analysis reveals significant plane-of-sky rotation in Praesepe, with a mean velocity of 0.132 ± 0.022 km s−1 in a clockwise direction.

scholarly journals Commission 33. (Stellar Statistics.)

1936 ◽  
Vol 5 ◽  
pp. 343-344
Author(s):  
B. Lindblad ◽  
C. Schalén
Keyword(s):  
Open Clusters ◽  
Radial Velocities ◽  
General Assembly ◽  
Proper Motions ◽  
The Future ◽  
The Subject

A recommendation to the Union concerning the construction of certain tables was accepted.A discussion was opened on the subject of collaboration in the study of open clusters. An application to the General Assembly was passed for a recommendation as follows: “That the Union call attention to the important problems connected with the open clusters and determinations of proper motions, radial velocities, magnitudes and spectra along the lines already inaugurated at several observatories.”It was agreed that Dr Mineur should approach the observatories of the Carte du Ciel on the subject of photographing the open clusters for the future determinations of proper motions.

scholarly journals The Status of Absolute Proper Motions and the Kinematics of Globular Clusters

1995 ◽  
Vol 164 ◽  
pp. 406-406 ◽  
Author(s):  
M. Geffert ◽  
B. Dauphole ◽  
J. Colin ◽  
M. Odenkirchen ◽  
H.-J. Tucholke ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Radial Velocities ◽  
Proper Motions ◽  
Preliminary Results ◽  
Space Motion ◽  
The Status ◽  
Galactic Potentials ◽  
Total Energies

We have studied a sample of 26 globular clusters for which so far absolute proper motions exist in the literature. The proper motions were combined with distances and radial velocities for a determination of the space motion of the clusters. Using different galactic potentials (see Dauphole & Colin 1994 and references therein) we calculated the orbits of the globular clusters and their time averaged eccentricities, total energies, and apo- and perigalactic distances. The relation of the orbital quantities to the metallicities of the globular clusters has been studied. Preliminary results of this study were presented in Geffert et al. (1993).

scholarly journals Determination of proper motions and membership of the open clusters NGC 1750 and NGC 1758

1998 ◽  
Vol 131 (1) ◽  
pp. 89-98 ◽  
Author(s):  
K.-P. Tian ◽  
J.-L. Zhao ◽  
Zh.-Y. Shao ◽  
P. B. Stetson
Keyword(s):  
Open Clusters ◽  
Proper Motions

scholarly journals Determination of proper motions and membership of the open clusters NGC 1817 and NGC 1807

1998 ◽  
Vol 133 (3) ◽  
pp. 387-394 ◽  
Author(s):  
L. Balaguer-Núñez ◽  
K. P. Tian ◽  
J. L. Zhao
Keyword(s):  
Open Clusters ◽  
Proper Motions

scholarly journals A new compact young moving group around V1062 Scorpii

2018 ◽  
Vol 614 ◽  
pp. A81 ◽  
Author(s):  
Siegfried Röser ◽  
Elena Schilbach ◽  
Bertrand Goldman ◽  
Thomas Henning ◽  
Attila Moor ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Proper Motion ◽  
Near Infrared ◽  
Open Clusters ◽  
Radial Velocities ◽  
The Sun ◽  
Velocity Measurements ◽  
Trigonometric Parallaxes ◽  
The Mean ◽  
Moving Groups

Aims. We are searching for new open clusters or moving groups in the solar neighbourhood. Methods. We used the Gaia-TGAS catalogue, cut it into narrow proper motion and parallax slices and searched for significant spatial over-densities of stars in each slice. We then examined stars forming over-densities in optical and near-infrared colour-magnitude diagrams to determine if they are compatible with isochrones of a cluster. Results. We detected a hitherto unknown moving group or cluster in the Upper Centaurus Lupus (UCL) section of the Scorpius-Centaurus OB association (Sco-Cen) at a distance of 175 pc from the Sun. It is a group of 63 comoving stars of less than 10 to about 25 Myr in age. For the brightest stars that are present in the Gaia-TGAS catalogue, the mean difference between kinematic and trigonometric distance moduli is − 0.01 mag with a standard deviation of 0.11 mag. Fainter cluster candidates are found in the HSOY catalogue, where no trigonometric parallaxes are available. For a subset of our candidate stars, we obtained radial velocity measurements at the MPG/ESO 2.2 m telescope in La Silla. Altogether we found 12 members with confirmed radial velocities and parallaxes, 31 with parallaxes or radial velocities, and 20 candidates from the convergent point method. The isochrone masses of our 63 members range from 2.6 to 0.7 M⊙.

scholarly journals Chemical tagging experiment with the Gaia-ESO open clusters

2017 ◽  
Vol 13 (S334) ◽  
pp. 128-131
Author(s):  
Rodolfo Smiljanic ◽  
Keyword(s):  
Chemical Composition ◽  
Open Cluster ◽  
Open Clusters ◽  
Proper Motions ◽  
Preliminary Results ◽  
Abundance Patterns ◽  
Similar Chemical ◽  
Chemical Tagging ◽  
The Mean ◽  
Using Data

AbstractStars observed in the field of an open cluster are ideal for a controlled test of chemical tagging. Using chemical tagging, one should identify the cluster members, i.e., those stars of similar chemical composition, if their composition is indeed different from that of all the non-member stars of the field. Moreover, the abundance-based membership can be checked against membership based on radial velocities and proper motions. Here, I report preliminary results of such an experiment using data from the Gaia-ESO Survey. Although the three membership criteria usually agree, a few interesting examples of discrepant membership classification have been found. In addition, the mean composition of each open cluster was compared to a sample of 1 600 Gaia-ESO field stars. Some cases of field stars with abundances matching those of the open clusters were identified. This experiment suggests that open clusters do not necessarily have unique abundance patterns that set them apart from all other clusters.

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