BVI CCD photometry of the broad main-sequence globular cluster NGC 1851

1990 ◽  
Vol 99 ◽  
pp. 817 ◽  
Author(s):  
Gonzalo Alcaino ◽  
William Liller ◽  
Franklin Alvarado ◽  
Erich Wenderoth
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
Ccd Photometry

scholarly journals The Abundance of the LMC Globular Cluster NGC 2213

1988 ◽  
Vol 126 ◽  
pp. 579-580
Author(s):  
Doug Geisler
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
High Accuracy ◽  
Magellanic Cloud ◽  
New Technique ◽  
Distance Modulus ◽  
Ccd Photometry ◽  
Cloud Clusters ◽  
A New Technique ◽  
Using Data

A new technique for determining accurate abundances in distant giants - Washington CCD photometry - has been applied to the intermediate-age LMC globular cluster NGC 2213. An abundance of −0.40 ± 0.15 was found from the analysis of 42 giants with V < 20, using data obtained with the 1.5 m telescope. Combined with published main-sequence photometry, the derived abundance indicates a true LMC distance modulus of 18.2 ± 0.2. A likely CN strong giant near the tip of the giant branch is identified. Abundances are also derived for a sample of 27 field giants. Results indicate that one could determine both the age and abundance of Magellanic Cloud clusters with high accuracy from Washington photometry using the 4 m in less than one hour of observing time per cluster.

scholarly journals Pal 1: A Globular Cluster Anyway?

1995 ◽  
Vol 164 ◽  
pp. 395-395
Author(s):  
J. Borissova ◽  
N. Spassova
Keyword(s):  
Globular Cluster ◽  
Luminosity Function ◽  
Main Sequence ◽  
Structural Parameters ◽  
Distance Modulus ◽  
Horizontal Branch ◽  
Ccd Photometry ◽  
Horizontal Branch Stars ◽  
Mass Estimate

CCD photometry of the halo cluster Pall in Thuan-Gunn system is presented. The color - magnitude diagrams (Fig. 1) show a well defined red horizontal branch, lower giant branch and main-sequence down to about two magnitudes below the main-sequence turnoff. The giant branch is absent and the brightest stars are horizontal-branch stars. The horizontal branch is composed of red stars only. The age of the cluster, determined by comparison with the isochrones of Bell and Vanden Berg (1987) is consistent with an age between 12 – 14 Gyr. and a metallicity [Fe/H] = −0.79. The observed luminosity function shows a deficiency of stars from about 0.5 mag below turnoff up to g = 21 mag. A distance modulus of (m – M)g0 = 15.35 ± 0.1 magnitude has been derived. An estimate of the cluster structural parameters gives rc = 1.7 pc and c = 1.46. A mass estimate of 1.6 × 103M⊙ and mass-to-light ratio 1.77 has been obtained, using King's (1966) method.

scholarly journals CCD Photometry in the Globular Cluster M4

1995 ◽  
Vol 164 ◽  
pp. 411-411
Author(s):  
W.K. Griffiths ◽  
I.N. Kanatas ◽  
R.J. Dickens ◽  
A.J. Penny
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
Ccd Photometry ◽  
Magnitude Diagram ◽  
Red Giant

A V, B- V composite colour-magnitude diagram, based upon CCD photometry from V~ 12 on the red giant branch to V~ 25 on the main-sequence has been derived for the globular cluster M4. A distance to the cluster of (m – M)v = 12.84 ± 0.19 is determined and the best match to theoretical isochrones is for the case [Fe/H]=−1.27 and an age of 16±1 Gyr. A differential age comparison with NGC 362 shows that M4 is approximately 1.7 Gyr older.

scholarly journals UBVI CCD Photometry of an old Open Cluster AM-2

1996 ◽  
Vol 169 ◽  
pp. 435-436 ◽  
Author(s):  
Myung Gyoon Lee
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
Open Cluster ◽  
Ultraviolet Excess ◽  
Galactic Latitude ◽  
Ccd Photometry ◽  
Fitting Method ◽  
Age Ratio ◽  
Red Giant Clump ◽  
Red Giant

AM-2 is a sparse cluster located at low galactic latitude. It has been suspected to be a globular cluster. We present a study of AM-2 based on the deep UBVI CCD photometry obtained using the Las Campanas duPont 2.5m telescope. The color-magnitude diagrams of AM-2 show (a) a main-sequence extending up to V ≈ 19 mag at (B – V) ≈ 1.1 mag, (b) a small number of red giant clump giants, (c) the brightest red giant at V ≈ 16.1 mag and (B – V) ≈ 1.9 mag, and (d) a small group of mysterious blue stars at V ≈ 16.6 mag and (B – V) ≈ 0.9 mag. We have estimated the reddening using the color-color diagram, E(B – V) = 0.56 ± 0.04. The metallicity of the main-sequence stars has been estimated from the ultraviolet excess, δ(U – B)0.6 = 0.09 ± 0.04, to be [Fe/H] = −0.4 ± 0.2 dex. The distance to the cluster has been measured using the Zero-Age-Main-Sequence fitting method, (m – M)0 = 14.8 ± 0.3 (d = 9.1 ± 1.4 kpc). Finally we have estimated the age of the cluster using the Revised Yale isochrones and the Morphological Age Ratio (MAR) method, obtaining a value of 5 ± 1 Gyrs (Fig. 1). This shows that AM-2 is not a globular cluster, but an old open cluster.

scholarly journals Main-sequence CCD photometry of the globular cluster   Centauri

1991 ◽  
Vol 250 (2) ◽  
pp. 314-339 ◽  
Author(s):  
R. G. Noble ◽  
R. J. Dickens ◽  
J. Buttress ◽  
W. K. Griffiths ◽  
A. J. Penny
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
Ccd Photometry

scholarly journals Deep CCD Photometry in M 5

1988 ◽  
Vol 126 ◽  
pp. 623-623
Author(s):  
Harvey B. Richer ◽  
Gregory G. Fahlman
Keyword(s):  
Excellent Agreement ◽  
Globular Cluster ◽  
Main Sequence ◽  
Ccd Photometry ◽  
Upper Limit ◽  
Luminosity Functions ◽  
Magnitude Diagram ◽  
Metal Abundance ◽  
Mass Segregation

Deep UBV CCD imagery has been obtained in three fields of the galactic globular cluster M5. The locations of these fields are at distances of 8, 21, and 58 core radii. In the middle field, which overlaps substantially with the deep photometry field of Arp, the CCD photometry reaches fainter than V = 26. Color-magnitude diagrams constructed from stars in the inner two fields are identical, to within the errors, and can be used to set an upper limit of 4% to any metallicity difference between these two fields. A U, (U - V) color-magnitude diagram is also shown for the inner field and compared with that of a more metal rich and more metal poor cluster. Major differences in the morphology of these three diagrams are present as a function of metal abundance. From the color-color diagram the reddening in the direction of M5 is determined (E(B - V) = 0.02) as well as its metallicity ([M/H] = −1.13). The distance to M5 is then established from fitting local subdwarfs to the lower main sequence of the cluster. This yields (m - M)V = 14.3. Using the observationally determined parameters, an overlay of the appropriate VandenBerg and Bell isochrones yields an age estimate of 18 Gyrs for M5. Luminosity functions constructed from the three fields show excellent agreement through the range V = 17 to 23. Fainter than V = 23 there is some evidence for mass segregation effects due to dynamical relaxation.

scholarly journals On the origin of the helium-rich population in the peculiar globular cluster Omega Centauri

2009 ◽  
Vol 5 (S268) ◽  
pp. 187-188
Author(s):  
Donatella Romano ◽  
M. Tosi ◽  
M. Cignoni ◽  
F. Matteucci ◽  
E. Pancino ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Globular Cluster ◽  
Main Sequence ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Potential Well ◽  
Galactic Winds ◽  
Supernova Explosions

AbstractIn this contribution we discuss the origin of the extreme helium-rich stars which inhabit the blue main sequence (bMS) of the Galactic globular cluster Omega Centauri. In a scenario where the cluster is the surviving remnant of a dwarf galaxy ingested by the Milky Way many Gyr ago, the peculiar chemical composition of the bMS stars can be naturally explained by considering the effects of strong differential galactic winds, which develop owing to multiple supernova explosions in a shallow potential well.

scholarly journals Are Galactic globular cluster AGB stars rich or poor in Sodium? Sodium abundance of AGB and RGB stars in NGC 2808

2015 ◽  
Vol 12 (S316) ◽  
pp. 361-362
Author(s):  
Yue Wang ◽  
Francesca Primas ◽  
Corinne Charbonnel ◽  
Mathieu Van der Swaelmen ◽  
William Chantereau ◽  
...  
Keyword(s):  
Spectroscopic Study ◽  
Globular Cluster ◽  
Main Sequence ◽  
Significant Fraction ◽  
Agb Stars ◽  
2Nd Generation ◽  
Red Giant ◽  
Sodium Abundance

AbstractA spectroscopic study comparing the [Na/Fe] distributions of RGB and AGB stars in the Galactic globular cluster (GC) NGC 6752 found that there was no Na-rich, 2nd-generation star along the early-AGB of this cluster. This came as a surprise since in this GC, as well as other Galactic GCs studied so far, 1st- and 2nd-generation stars have usually been found from the main sequence turnoff up to the red giant branch. To investigate whether the failure of a significant fraction of stars to ascend the AGB also happens to other GCs, we studied a sample of AGB and RGB stars in NGC 2808 observed at the ESO/VLT with FLAMES. Contrary to NGC 6752, we find that the AGB and RGB stars we studied in NGC 2808 have comparable [Na/Fe] dispersions.

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