Light-element chemistry and the double red giant branch in the galactic globular cluster NGC 288

Tiffany Hsyu, R. Michael Rich, Christian I. Johnson, Young Wook Lee

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The globular cluster NGC 288 was previously reported to exhibit two distinct red giant branches (RGBs) in the narrowband calcium (HK) and Strömgren b- and y-band passes. In order to investigate this phenomenon further, we obtained moderate resolution (R ~ 18, 000) spectra of 27 RGB stars in NGC 288 with the Hydra multifiber spectrograph on the Blanco 4 m telescope at Cerro Tololo Inter-American Observatory (CTIO). From these data we derive iron (〈[Fe/H]〉 = -1.19; σ = 0.12), oxygen (〈[O/Fe]〉 = +0.25; σ = 0.13), and sodium (〈[Na/Fe]〉 = +0.15; σ = 0.26) abundances using standard equivalent width and spectrum synthesis techniques. Combining these data with those available in the literature indicates that the two giant branches have distinctly different light-element chemistry but do not exhibit a significant spread in [Fe/H]. A new transmission tracing for the CTIO Ca filter, obtained for this project, shows that CN contamination is the primary spectral feature driving the split RGB. Interestingly, the CN leak in the current CTIO Ca filter may be used as an efficient means to search for CN-weak and CN-strong stars in systems with otherwise small Ca abundance variations.

Original languageEnglish
Pages (from-to)597-604
Number of pages8
JournalPublications of the Astronomical Society of the Pacific
Volume126
Issue number941
DOIs
Publication statusPublished - 2014 Jul

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light elements
globular clusters
observatories
observatory
chemistry
Hydra
filter
filters
stars
tracing
spectrographs
narrowband
calcium
contamination
sodium
telescopes
iron
oxygen
synthesis

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

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title = "Light-element chemistry and the double red giant branch in the galactic globular cluster NGC 288",
abstract = "The globular cluster NGC 288 was previously reported to exhibit two distinct red giant branches (RGBs) in the narrowband calcium (HK) and Str{\"o}mgren b- and y-band passes. In order to investigate this phenomenon further, we obtained moderate resolution (R ~ 18, 000) spectra of 27 RGB stars in NGC 288 with the Hydra multifiber spectrograph on the Blanco 4 m telescope at Cerro Tololo Inter-American Observatory (CTIO). From these data we derive iron (〈[Fe/H]〉 = -1.19; σ = 0.12), oxygen (〈[O/Fe]〉 = +0.25; σ = 0.13), and sodium (〈[Na/Fe]〉 = +0.15; σ = 0.26) abundances using standard equivalent width and spectrum synthesis techniques. Combining these data with those available in the literature indicates that the two giant branches have distinctly different light-element chemistry but do not exhibit a significant spread in [Fe/H]. A new transmission tracing for the CTIO Ca filter, obtained for this project, shows that CN contamination is the primary spectral feature driving the split RGB. Interestingly, the CN leak in the current CTIO Ca filter may be used as an efficient means to search for CN-weak and CN-strong stars in systems with otherwise small Ca abundance variations.",
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Light-element chemistry and the double red giant branch in the galactic globular cluster NGC 288. / Hsyu, Tiffany; Michael Rich, R.; Johnson, Christian I.; Lee, Young Wook.

In: Publications of the Astronomical Society of the Pacific, Vol. 126, No. 941, 07.2014, p. 597-604.

Research output: Contribution to journalArticle

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