scholarly journals Results from Three Dimensional Spectral Classification of Population II Stars Using the DDO Photometric System

1973 ◽  
Vol 50 ◽  
pp. 176-182
Author(s):  
W. Osborn
Keyword(s):  
Globular Clusters ◽  
Three Dimensional ◽  
Photometric System ◽  
Horizontal Branch ◽  
Intermediate Band ◽  
Theoretical Predictions ◽  
The Mean ◽  
Red Giant ◽  
The Masses

The David Dunlap Observatory (DDO) intermediate-band photometric system described in the previous paper has been used to observe a number of red giant branch, horizontal branch, and asymptotic branch members in each of the five globular clusters M3, M5, M10, M13, and M92. A calibration of the DDO system is described by which it was possible to determine the effective temperatures, surface gravities, [Fe/H] values, and masses of the observed stars. The mean [Fe/H] values for the clusters were found to be −1.01 for M3, −0.68 for M5, −1.44 for M10, −1.69 for M13, and −1.96 for M92. Evidence was found that the masses of the horizontal branch and asymptotic branch stars are systematically smaller than those of red giant branch members. Two stars were discovered to have CN bands that are anomalously strong for Population II objects. The observational results have been compared with the theoretical predictions of two detailed Population II evolutionary tracks and in general the agreement is good.

scholarly journals Photometric Classification of Stars in the Vilnius Observatory

1973 ◽  
Vol 50 ◽  
pp. 183-185 ◽  
Author(s):  
V. Straižys
Keyword(s):  
Spatial Distribution ◽  
Chemical Composition ◽  
Stellar Evolution ◽  
Three Dimensional ◽  
Point Of View ◽  
Photometric System ◽  
Intermediate Band ◽  
Dimensional Classification

The programs of three-dimensional classification of stars using eight-color intermediate band photometric system are described. They include (1) investigation of interstellar reddening and absorption in the direction of objects significant from point of view of stellar evolution, (2) investigation of spatial distribution of stars of different spectral classes, luminosities and chemical composition, (3) the detection of unique objects.

scholarly journals Horizontal Branch Evolution and RR Lyrae Star Pulsation

1995 ◽  
Vol 10 ◽  
pp. 590-593 ◽  
Author(s):  
Arthur N. Cox
Keyword(s):  
Stellar Evolution ◽  
Globular Clusters ◽  
Deep Convection ◽  
Big Bang ◽  
Helium Abundance ◽  
Horizontal Branch ◽  
Rr Lyrae ◽  
Red Giant ◽  
The Masses ◽  
The Big Bang

For many years there has been a confrontation between stellar evolution and pulsation theories concerning the masses, luminosities, and compositions of the horizontal branch RR Lyrae variables. Masses obtained by Cox, Hodson & Clancy (CHC, 1983) were very low, but Kovacs (1985) and later Kovacs & Buchler (1988) suggested somewhat larger ones. Even later Simon & Cox (1991) verified CHC results, though still using the Los Alamos opacities. Petersen (1991, 1992) has also discussed this mass problem in some detail. The persistent discrepancy of 0.1 Mʘ or more between the evolution and pulsation masses was mostly ignored because neither theory could find any significant flaw in its analysis. Cox (1991), Kovacs, Buchler & Marom (1991), and Kovacs, Buchler, Marom, Iglesias & Rogers (1992) finally showed that larger double-mode pulsation masses, are consistent with evolution calculations to reproduce color-magnitude diagrams of globular clusters. Evolution tracks by many for years, especially the recent ones by Lee, Demarque & Zinn (1990), did require a much lower primordial helium abundance near the big bang value near Y = 0.23, and now this value, slightly enhanced by deep convection dredge-up in the earlier red giant stage, is also found to be appropriate for pulsation studies.

scholarly journals Constant mean curvature spheres in homogeneous three-manifolds

2020 ◽  
Author(s):  
William H. Meeks ◽  
Pablo Mira ◽  
Joaquín Pérez ◽  
Antonio Ros
Keyword(s):  
Mean Curvature ◽  
Constant Mean Curvature ◽  
Three Dimensional ◽  
Complete Classification ◽  
Homogeneous Manifolds ◽  
The Mean

Abstract We prove that two spheres of the same constant mean curvature in an arbitrary homogeneous three-manifold only differ by an ambient isometry, and we determine the values of the mean curvature for which such spheres exist. This gives a complete classification of immersed constant mean curvature spheres in three-dimensional homogeneous manifolds.

scholarly journals Observations of low mass stars in clusters: Some constraints and puzzles for stellar evolution theory

1984 ◽  
Vol 105 ◽  
pp. 123-138
Author(s):  
R.D. Cannon
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Star Clusters ◽  
Variable Stars ◽  
Open Clusters ◽  
Low Mass Stars ◽  
Theory Of Evolution ◽  
Theoretical Predictions ◽  
Low Mass ◽  
Red Giant

This review will attempt to do two things: (i) discuss some of the data which are available for testing the theory of evolution of low mass stars, and (ii) point out some problem areas where observations and theory do not seem to agree very well. This is of course too vast a field of research to be covered in one brief review, so I shall concentrate on one particular aspect, namely the study of star clusters and especially their colour-magnitude (CM) diagrams. Star clusters provide large samples of stars at the same distance and with the same age, and the CM diagram gives the easiest way of comparing theoretical predictions with observations, although crucial evidence is also provided by spectroscopic abundance analyses and studies of variable stars. Since this is primarily a review of observational data it is natural to divide it into two parts: (i) galactic globular clusters, and (ii) old and intermediate-age open clusters. Some additional evidence comes from Local Group galaxies, especially now that CM diagrams which reach the old main sequence are becoming available. For each class of cluster I shall consider successive stages of evolution from the main sequence, up the hydrogen-burning red giant branch, and through the helium-burning giant phase.

scholarly journals Red Variable Stars in Metal Rich Globular Clusters

1973 ◽  
Vol 21 ◽  
pp. 151-163
Author(s):  
T. Lloyd Evans ◽  
J. W. Menzies
Keyword(s):  
Systematic Study ◽  
Globular Clusters ◽  
Variable Stars ◽  
Large Numbers ◽  
Magnitude Diagram ◽  
Metal Abundance ◽  
The Mean ◽  
Red Giant ◽  
Photoelectric Observations ◽  
Considerable Range

The globular clusters contain sufficiently large numbers of stars to permit a systematic study of the intrinsically rare variable stars which lie near the tip of the red giant branch. The position of the smaller amplitude stars in the colour magnitude diagram is of particular interest. Eggen (1972) has published photoelectric observations of such stars in several globular clusters, most of intermediate or low metal abundance. The mean colour of 14 stars in 5 clusters is (V-IK) = 1.40, with a spread from 1.60 to 1.12 (or 0.75 if V8 in M22 is of this type) which Eggen regards as indicating a range of temperature. The red variable stars in the metal rich globular cluster 47 Tucanae are much redder and show a considerable range of colour.

scholarly journals Synthetic spectroscopic indices for identifying multiple stellar populations in globular clusters

2020 ◽  
Vol 493 (2) ◽  
pp. 2195-2206
Author(s):  
Emanuele Bertone ◽  
Miguel Chávez ◽  
J César Mendoza
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Stellar Populations ◽  
Stellar Model ◽  
Chemical Compositions ◽  
Horizontal Branch ◽  
Atmospheric Parameters ◽  
Data Set ◽  
Spectral Diagnostics ◽  
Red Giant

ABSTRACT We present an investigation of synthetic spectroscopic indices that can plausibly help in identifying the presence of multiple stellar populations in globular clusters. The study is based on a new grid of stellar model atmospheres and high-resolution (R  = 500 000) synthetic spectra, that consider chemical partitions that have been singled out in Galactic globular clusters. The data base is composed of 3472 model atmospheres and theoretical spectra calculated with the collection of Fortran codes DFSYNTHE, ATLAS9 and SYNTHE, developed by Robert L. Kurucz. They cover a range of effective temperature from 4300 to 7000 K, surface gravity from 2.0 to 5.0 dex and four different chemical compositions. A set of 19 spectroscopic indices were calculated from a degraded version (R  = 2500) of the theoretical spectra data set. The set includes five indices previously used in the context of globular clusters analyses and 14 indices that we have newly defined by maximizing the capability of differentiating the chemical compositions. We explored the effects of atmospheric parameters on the index values and identified the optimal spectral diagnostics that allow to trace the signatures of objects of different stellar populations, located in the main sequence, the red giant branch and the horizontal branch. We found a suitable set of indices, that mostly involve molecular bands (in particular NH, but also CH and CN), that are very promising for spectroscopically identifying multiple stellar populations in globular clusters.

scholarly journals The Link between Chemical Anomalies along the Red Giant Branch and the Horizontal Branch Extension in Globular Clusters

2007 ◽  
Vol 671 (2) ◽  
pp. L125-L128 ◽  
Author(s):  
Eugenio Carretta ◽  
Alejandra Recio-Blanco ◽  
Raffaele G. Gratton ◽  
Giampaolo Piotto ◽  
Angela Bragaglia
Keyword(s):  
Globular Clusters ◽  
Horizontal Branch ◽  
Red Giant ◽  
Chemical Anomalies

scholarly journals Globular Clusters in the Vilnius Photometric System

1988 ◽  
Vol 126 ◽  
pp. 515-516
Author(s):  
K. Zdanavičius
Keyword(s):  
Globular Clusters ◽  
Photometric System ◽  
Two Dimensional ◽  
Halo Stars ◽  
Dimensional Classification

The Vilnius photometric system was developed for photometric two-dimensional classification of stars and for the determination of interstellar reddening. The system consists of seven magnitudes U, P, X, Y, Z, V and S with mean wavelengths of 345, 375, 405, 466, 516, 544 and 655 nm and half-widths of the order 20 – 30 nm (Straižys 1977). Later on the system was successfully used for the determination of temperatures and the metallicities of halo stars (Bartkevičius and Sperauskas 1983).

scholarly journals Precision CCD Photometry of the Horizontal Branch

1995 ◽  
Vol 167 ◽  
pp. 361-362
Author(s):  
A. G. Davis Philip
Keyword(s):  
Globular Clusters ◽  
Photometric System ◽  
Horizontal Branch ◽  
Ccd Photometry ◽  
Horizontal Branch Stars ◽  
Color System

The Strömgren four-color system is well suited to the measure and analysis of horizontal-branch stars. The increased accuracy of the CCD photometric system and the ability to measure fainter stars in very crowded regions make the combination of the CCD system and four-color photometry an excellent one to study horizontal-branch stars in globular clusters.

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