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 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 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 An attempt to Derive the Proper Motion for Blanco Cluster 1

1995 ◽  
Vol 148 ◽  
pp. 232-233
Author(s):  
Bambang Hidayat ◽  
Paulus Wiyanto
Keyword(s):  
Proper Motion ◽  
Milky Way ◽  
High Ratio ◽  
Open Clusters ◽  
Photometric Data ◽  
Point Of View ◽  
Large Field ◽  
Small Field ◽  
Proper Motions ◽  
Field Solution

In order to establish the probability of physical membership of open clusters by means of astrometrical methods, two criteria are used: the position distribution of stars in the sky and their proper motions. Proper motion methods have shown validity from a practical point of view; but are difficult to apply where there is a high ratio of cluster-to-field stars, and in crowded fields of the Milky Way.As a test we have selected the nearby (170–190 pc) Blanco Cluster 1 (1 = 16°, b = −73°) in order to avoid complications arising from crowded fields. Photometric data however, suggests that the diameter of the cluster is rather extended (~ 120 arcsec). This will require a large-field solution, rather than a small-field solution which can be obtained with greater accuracy using Schmidt astrometry (Fresneau 1978; Nakamura & Sekiguchi 1993).

scholarly journals Nearby Open Clusters and HR Diagram Calibration

1998 ◽  
Vol 11 (1) ◽  
pp. 579-579
Author(s):  
N. Robichon ◽  
F. Arenou ◽  
C. Turon ◽  
Y. Lebreton ◽  
J.-C. Mermilliod
Keyword(s):  
Open Clusters ◽  
Photometric Data ◽  
Proper Motions ◽  
Helium Content ◽  
Intermediate Data ◽  
The Mean ◽  
Cluster A ◽  
Selection Of ◽  
Hr Diagram

13 clusters have been analysed (Coma Ber, the Pleiades, IC 2602, IC 2391, Praesepe, Alpha Per, NGC 6475, Blanco 1, Stock 2, NGC 6633, IC 4756, NGC 2516 and NGC 3532). Cluster members have been selected using Hipparcos proper motions and parallaxes. The mean cluster parallaxes have been determined using Hipparcos intermediate data (abscissae on the Reference Great Circles) taking into account star to star correlations. Both selection of members and computation of cluster mean parallaxes are described in Mermilliod et al., 1997 and Robichon et al., 1997. For each cluster, a selection of fainter stars in the ‘Base des Amas’ (Mermilliod, 1988), based on photometric data as well as radialvelocities and proper motions when available, has been done. From this selection and the computed mean parallaxes, the location of the 13 cluster sequences in the observational HR diagram is derived very accurately, at least for the closest clusters for which good photometry and small errors on the mean parallaxes are available. Relative positions of cluster sequences cannot only be explained by differences between cluster metallicities. For example, the Pleiades sequence is 0.5 magnitude bellow the Praesepe sequence whereas the adopted metallicities (obtained spectroscopically i.e. whithout any assumption on the helium content) are respectively -0.034 and +0.10.

scholarly journals Characterising open clusters in the solar neighbourhood with the Tycho-Gaia Astrometric Solution

2018 ◽  
Vol 615 ◽  
pp. A49 ◽  
Author(s):  
T. Cantat-Gaudin ◽  
A. Vallenari ◽  
R. Sordo ◽  
F. Pensabene ◽  
A. Krone-Martins ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Markov Chain ◽  
High Probability ◽  
Open Clusters ◽  
Distance Modulus ◽  
The Sun ◽  
Proper Motions ◽  
Orbital Parameters ◽  
Naval Observatory ◽  
Galactic Potential

Context. The Tycho-Gaia Astrometric Solution (TGAS) subset of the first Gaia catalogue contains an unprecedented sample of proper motions and parallaxes for two million stars brighter than G ~ 12 mag. Aims. We take advantage of the full astrometric solution available for those stars to identify the members of known open clusters and compute mean cluster parameters using either TGAS or the fourth U.S. Naval Observatory CCD Astrograph Catalog (UCAC4) proper motions, and TGAS parallaxes. Methods. We apply an unsupervised membership assignment procedure to select high probability cluster members, we use a Bayesian/Markov Chain Monte Carlo technique to fit stellar isochrones to the observed 2MASS JHKS magnitudes of the member stars and derive cluster parameters (age, metallicity, extinction, distance modulus), and we combine TGAS data with spectroscopic radial velocities to compute full Galactic orbits. Results. We obtain mean astrometric parameters (proper motions and parallaxes) for 128 clusters closer than about 2 kpc, and cluster parameters from isochrone fitting for 26 of them located within a distance of 1 kpc from the Sun. We show the orbital parameters obtained from integrating 36 orbits in a Galactic potential.

scholarly journals Proper motions of open clusters within 1 kpc based on the TYCHO2 Catalogue

2001 ◽  
Vol 376 (2) ◽  
pp. 441-447 ◽  
Author(s):  
W. S. Dias ◽  
J. R. D. Lépine ◽  
B. S. Alessi
Keyword(s):  
Open Clusters ◽  
Proper Motions

scholarly journals The Bologna Open Cluster Chemical Evolution project: a large, homogeneous sample of Galactic open clusters

2008 ◽  
Vol 4 (S258) ◽  
pp. 153-160
Author(s):  
Angela Bragaglia
Keyword(s):  
Chemical Evolution ◽  
Galactic Disk ◽  
Open Cluster ◽  
Open Clusters ◽  
Photometric Data ◽  
Homogeneous Sample ◽  
Metallicity Distribution

AbstractThe Bologna Open Cluster Chemical Evolution (BOCCE) project is a photometric and spectroscopic survey of open clusters, to be used as tracers of the Galactic disk properties and evolution. The clusters parameters (age, distance, reddening, metallicity, and detailed abundances) are derived in a precise and homogeneous way. This will contribute to a solid, reliable description of the disk: the clusters parameters will be used, for instance, to determine the metallicity distribution in the Galactic disk and how it has evolved with time. We have concentrated on old open clusters and we have presently in our hands data for about 40 open clusters; we have fully analyzed the photometric data for about one half of them and the spectra for one quarter of them.

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