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.

scholarly journals Photometric Classification of Blue Horizontal-Branch Stars

1973 ◽  
Vol 50 ◽  
pp. 230-244
Author(s):  
A. G. Davis Philip
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Lower Surface ◽  
The Other ◽  
Horizontal Branch ◽  
Horizontal Branch Stars ◽  
Color System ◽  
General Field ◽  
Effective Temperatures

The Strömgren four-color system has been used to classify blue horizontal-branch stars in globular clusters and in the general field. A relation between δ log g (log gmain sequence–log gstar) and δc1 (c1observed–c1main sequence) has been determined which gives log g to within ±0.2 for stars with log g's between 4.4 and 2.0. Newell (1970) has determined a relation between (B–V)0 and θe. Thus the gravities and effective temperatures of blue horizontal-branch stars can be determined from photometric measures alone. Five globular clusters have been studied at the present time. The BHB stars in the globular cluster M3 and M13 have lower surface gravities than BHB stars in the other clusters studied. Iben and Rood (1970) have recently suggested that the BHB stars of M3 may have lost more mass than BHB stars in more metal poor clusters.

scholarly journals Photometric Evidence for Mixing and Diffusion in GC Stars

2002 ◽  
Vol 12 ◽  
pp. 273-275
Author(s):  
Frank Grundahl
Keyword(s):  
Globular Clusters ◽  
Horizontal Branch ◽  
Mixing Processes ◽  
Ccd Photometry ◽  
Present Evidence ◽  
Horizontal Branch Stars ◽  
Internal Mixing ◽  
And Diffusion

AbstractBased on StrömgrenuvbyCCD photometry, and UVES spectroscopy we present evidence that possibly all globular clusters show large variations in their abundances of nitrogen, aluminium and sodium, which are not only due to internal mixing processes. Furthermore the evidence for radiative levitation among hot horizontal branch stars is briefly discussed.

Super-Helium-rich Populations and the Origin of Extreme Horizontal-Branch Stars in Globular Clusters

2005 ◽  
Vol 621 (1) ◽  
pp. L57-L60 ◽  
Author(s):  
Young-Wook Lee ◽  
Seok-Joo Joo ◽  
Sang-Il Han ◽  
Chul Chung ◽  
Chang H. Ree ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Horizontal Branch ◽  
Horizontal Branch Stars

scholarly journals Study of the Helium Enrichment in Globular Clusters

2009 ◽  
Vol 5 (S262) ◽  
pp. 27-30
Author(s):  
Aldo A. R. Valcarce ◽  
Márcio Catelan
Keyword(s):  
High Precision ◽  
Globular Clusters ◽  
Stellar Populations ◽  
Horizontal Branch ◽  
Previous Generation ◽  
Horizontal Branch Stars

AbstractGlobular clusters (GCs) are spheroidal concentrations typically containing of the order of 105 to 106, predominantly old, stars. Historically, they have been considered as the closest counterparts of the idealized concept of “simple stellar populations.” However, some recent observations suggest than, at least in some GCs, some stars are present that have been formed with material processed by a previous generation of stars. In this sense, it has also been suggested that such material might be enriched in helium, and that blue horizontal branch stars in some GCs should accordingly be the natural progeny of such helium-enhanced stars. In this contribution we show that, at least in the case of M3 (NGC 5272), the suggested level of helium enrichment is not supported by the available, high-precision observations.

Spectral Analysis of Supra Horizontal Branch Stars in Globular Clusters

White Dwarfs ◽  
2003 ◽  
pp. 155-156
Author(s):  
M. Ramspeck ◽  
U. Heber ◽  
S. Moehler ◽  
I. N. Reid
Keyword(s):  
Spectral Analysis ◽  
Globular Clusters ◽  
Horizontal Branch ◽  
Horizontal Branch Stars

scholarly journals On the Interpretation of RR Lyrae Properties in Globular Clusters and in Other Population II Systems

1973 ◽  
Vol 21 ◽  
pp. 197-206
Author(s):  
V. Castellani ◽  
P. Giannone ◽  
A. Renzini
Keyword(s):  
Mass Loss ◽  
Globular Clusters ◽  
Horizontal Branch ◽  
Rr Lyrae ◽  
Horizontal Branch Stars

AbstractThe differences in observational parameters of the RR Lyrae variables and horizontal branch stars of globular clusters and other population II systems are considered. A discontinuous behaviour of some parameters is outlined. The Oosterhoff dichotomy and the HB morphology are discussed with regard to a conjecture of mass loss in the pre-HB phase.

Setting Up of the Strömvil System Standards and Standard Regions

2003 ◽  
Vol 12 (4) ◽  
Author(s):  
A. G. Davis Philip ◽  
R. P. Boyle ◽  
V. Straižys ◽  
A. Kazlauskas
Keyword(s):  
Globular Clusters ◽  
Advanced Technology ◽  
Photometric System ◽  
Ccd Photometry ◽  
Primary Standards

AbstractCCD photometry of standard areas of the seven-color Strömvil photometric system in some open and globular clusters is described. The primary standards are being measured with a two-channel photoelectric photometer on the 1.5 meter telescope on Mt. Lemmon. CCD photometry of standard areas is in progress with the Vatican Advanced Technology Telescope on Mt. Graham and with the CASLEO 2.1 m telescope in Argentina. Two additional Strömvil projects are described.

Sign in / Sign up

Export Citation Format

Share Document