Sign on

SAO/NASA ADS Astronomy Abstract Service

· Find Similar Abstracts (with default settings below)
· Full Refereed Journal Article (PDF/Postscript)
· Full Refereed Scanned Article (GIF)
· References in the article
· Citations to the Article (30) (Citation History)
· Refereed Citations to the Article
· SIMBAD Objects (21)
· Reads History
· Translate This Page
The metal abundance of M28 and the occurrence of Cepheids in globular clusters
Smith, H. A.; Wehlau, A.
AA(Michigan State University, East Lansing), AB(Western Ontario, University, London, Canada)
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 298, Nov. 15, 1985, p. 572-580. NSERC-supported research. (ApJ Homepage)
Publication Date:
NASA/STI Keywords:
Cepheid Variables, Globular Clusters, Metallicity, Red Giant Stars, Stellar Spectra, Histograms, Horizontal Branch Stars, Star Distribution, Stellar Evolution
Bibliographic Code:


The metal abundance of the globular cluster M28 has been determined from low-resolution SIT-Vidicon spectra of red giants and RR Lyrae stars. The CN, Ca II H and K, and Ca I lambda4226 features in the red giant spectra indicate [M/H] = -1.0 ± 0.2. Delta-S measures of the RR Lyrae star spectra give [Fe/H] = -1.16 ± 0.2, in good agreement. Spectra of the variable star V7 show that it is probably not a U Geminorum star; it may not be a member of M28. The spectrum of the RV Tauri star V17 is briefly discussed. M28 is confirmed as one of the most metal-rich globular clusters known to contain type II Cepheid variable stars. The properties of the Cepheid-producing globular clusters are discussed. W Virginis-type Cepheids are most common among the most metal-rich globular clusters which also have blue horizontal branches. This predilection can be qualitatively explained by stellar evolution theory. There are 22 globular clusters with [Fe/H] > -1.8 which also have predominantly blue horizontal branches. Fourteen of these are known to contain type II Cepheids. These 14 clusters tend to have higher total visual luminosities, and hence larger stellar populations, than the eight clusters in which no Cepheids have been found. This is probably a result of the relatively brief lifetimes of globular cluster Cepheids: they are only represented in large stellar populations.

Printing Options

Print whole paper
Print Page(s) through

Return 600 dpi PDF to Acrobat/Browser. Different resolutions (200 or 600 dpi), formats (Postscript, PDF, etc), page sizes (US Letter, European A4, etc), and compression (gzip,compress,none) can be set through the Printing Preferences

More Article Retrieval Options

HELP for Article Retrieval

Bibtex entry for this abstract   Preferred format for this abstract (see Preferences)


Find Similar Abstracts:

Use: Authors
Keywords (in text query field)
Abstract Text
Return: Query Results Return    items starting with number
Query Form
Database: Astronomy
arXiv e-prints