scholarly journals On the Derivation of Abundances by Means of Features in the Sequences of the old Open Star Clusters

1976 ◽  
Vol 72 ◽  
pp. 97-99
Author(s):  
A. Maeder
Keyword(s):  
Metal Content ◽  
Main Sequence ◽  
Star Clusters ◽  
Open Star Clusters ◽  
Open Star ◽  
High Metal Content ◽  
High Metal ◽  
Magnitude Diagram ◽  
Homogeneous Models ◽  
Systematic Effects

Stellar evolution near the main-sequence is still subject to many discussions. In addition to the case of the cluster M 67 (Racine, 1971), quite systematic differences have been encountered during the comparison of theoretical isochrones and observed sequences in the colour-magnitude diagram of the old open star clusters (Maeder, 1974). In the case of M 67 and NGC 188, many attempts to discuss the characteristics of their sequences (such as the gap corresponding to the hydrogen-exhaustion phase) in terms of chemical composition have been made (e.g. Aizenman et al., 1969; Demarque and Schlesinger, 1969; Demarque and Heasley, 1971; Torres-Peimbert, 1971; Hejlesen et al., 1972; Caloi et al., 1974); some of these works have suggested to explain the gap parameters by a high metal content. Attemps to explain the differences between models and observations by means of simplified models with overshooting from convective cores have also been made (Maeder, 1973; Prather and Demarque, 1974). Let us also note that it has been shown that it is unlikely that the anomalies found are due to systematic effects, like the interstellar reddening, binarity, rotation or effects in calibrations or composition of the initial homogeneous models.

scholarly journals On Some Peculiar Features in the Sequences of the Old Open Star Clusters

1974 ◽  
Vol 59 ◽  
pp. 109-111
Author(s):  
A. Maeder
Keyword(s):  
Chemical Composition ◽  
Stellar Evolution ◽  
Main Sequence ◽  
Star Clusters ◽  
Open Star Clusters ◽  
Hydrogen Burning ◽  
The Core ◽  
Open Star ◽  
Solar Type ◽  
Good Agreement

In spite of the rather good agreement between the theory of stellar evolution and the observations, there exist some difficulties when one compares closely the sequences of open star clusters and the theoretical isochrones. Several, if not all, of the old open star clusters seem to be concerned, especially those which are accurately measured, namely Praesepe, NGC 2360, 752, 3680 and M67. The problem concerns the gap occuring in the HR diagram at the end of the phase of hydrogen burning in the core; it corresponds to the phase of hydrogen exhaustion (or of overall contraction). The sequence of M67 has been studied by Racine (1971) and Torres-Peimbert (1971). The well apparent gap is located farther from the zero-age main sequence than indicated by the models and the hook towards a larger Teff predicted during this phase is not observed. Differences in chemical composition may not be held responsible for these anomalies. From Torres-Peimbert's models, it may be assumed that neither solar type, nor super metal rich composition are able to reduce the discrepancies. As a further illustration, let us mention the case of NGC 752. In Table I, the main features related to the gap are examined: the disagreement, like in M67, essentially concern features 1 and 2. The observations are based on a recent study of Grenon and Mermillod (1973) and on Bell's data (1972). Bell has also mentioned the existence of discrepancies. As in M67, the gap is too far from the zero-age main sequence and does not present any sudden turning towards a larger Teff.

scholarly journals Massive open star clusters using the VVV survey

2012 ◽  
Vol 545 ◽  
pp. A54 ◽  
Author(s):  
A.-N. Chené ◽  
J. Borissova ◽  
J. R. A. Clarke ◽  
C. Bonatto ◽  
D. J. Majaess ◽  
...  
Keyword(s):  
Star Clusters ◽  
Open Star Clusters ◽  
Open Star

Photometric study of open star clusters in II quadrant: Teutsch 1 and Riddle 4

New Astronomy ◽  
2016 ◽  
Vol 42 ◽  
pp. 66-77 ◽  
Author(s):  
D. Bisht ◽  
R.K.S. Yadav ◽  
A.K. Durgapal
Keyword(s):  
Star Clusters ◽  
Photometric Study ◽  
Open Star Clusters ◽  
Open Star

scholarly journals A study of spatial structure of galactic open star clusters

2002 ◽  
Vol 383 (1) ◽  
pp. 153-162 ◽  
Author(s):  
Nilakshi ◽  
R. Sagar ◽  
A. K. Pandey ◽  
V. Mohan
Keyword(s):  
Spatial Structure ◽  
Star Clusters ◽  
Open Star Clusters ◽  
Open Star

scholarly journals Orbits of Open Star Clusters NGC 6067, NGC 2506 ANG IC 465

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Geeta Rangwal ◽  
R. K. S. Yadav ◽  
Alok K. Durgapal
Keyword(s):  
Proper Motion ◽  
Star Clusters ◽  
Open Star Clusters ◽  
Motion Data ◽  
Open Star ◽  
Galactic Clusters

The studies of the orbits of star clusters are very important to understand the evolution of these objects. The survival or dissolution of star clusters in galactic tides within which they orbit depends on their orbit history. The orbits of three galactic clusters namely NGC 6067, NGC 2506 and IC 4651 are calculated using newly available proper motion data taken from GAIA data. These orbits are traced backwards in time which is equal to the age of the clusters. The main parameters of the orbits such as eccentricity, apogalactic distance and perigalactic distance are calculated.

scholarly journals Interstellar Extinction in 20 Open Star Clusters

2017 ◽  
Vol 34 ◽  
Author(s):  
Geeta Rangwal ◽  
R. K. S. Yadav ◽  
Alok K. Durgapal ◽  
D. Bisht
Keyword(s):  
Spatial Variation ◽  
Star Clusters ◽  
Interstellar Extinction ◽  
Open Star Clusters ◽  
Circumstellar Material ◽  
Open Star ◽  
Near Ir ◽  
Spectral Class ◽  
Colour Excess ◽  
The Difference

AbstractThe interstellar extinction law in 20 open star clusters namely, Berkeley 7, Collinder 69, Hogg 10, NGC 2362, Czernik 43, NGC 6530, NGC 6871, Bochum 10, Haffner 18, IC 4996, NGC 2384, NGC 6193, NGC 6618, NGC 7160, Collinder 232, Haffner 19, NGC 2401, NGC 6231, NGC 6823, and NGC 7380 have been studied in the optical and near-IR wavelength ranges. The difference between maximum and minimum values of E(B − V) indicates the presence of non-uniform extinction in all the clusters except Collinder 69, NGC 2362, and NGC 2384. The colour excess ratios are consistent with a normal extinction law for the clusters NGC 6823, Haffner 18, Haffner 19, NGC 7160, NGC 6193, NGC 2401, NGC 2384, NGC 6871, NGC 7380, Berkeley 7, Collinder 69, and IC 4996. We have found that the differential colour-excess ΔE(B − V), which may be due to the occurrence of dust and gas inside the clusters, decreases with the age of the clusters. A spatial variation of colour excess is found in NGC 6193 in the sense that it decreases from east to west in the cluster region. For the clusters Berkeley 7, NGC 7380, and NGC 6871, a dependence of colour excess E(B − V) with spectral class and luminosity is observed. Eight stars in Collinder 232, four stars in NGC 6530, and one star in NGC 6231 have excess flux in near-IR. This indicates that these stars may have circumstellar material around them.

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