Journal
ASTROPHYSICAL JOURNAL LETTERS
Volume 733, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/2041-8205/733/2/L45
Keywords
globular clusters: individual (NGC 288); stars: abundances; stars: evolution
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Funding
- National Research Foundation of Korea
- AURA through the NSF [AST 0132798]
- National Research Foundation of Korea [과06A1403] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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We report the presence of two distinct red giant branches (RGBs) in the globular cluster NGC 288 from the narrowband calcium and Stromgren b and y photometry obtained at the CTIO 4 m Blanco telescope. The RGB of NGC 288 is clearly split into two in the hk [=(Ca - b) - (b - y)] index, while the split is not shown in the b - y color. Unlike other globular clusters with multiple populations reported thus far, the horizontal branch of NGC 288 is only mildly extended. Our stellar population models show that this and the presence of two distinct RGBs in NGC 288 can be reproduced if slightly metal-rich (Delta[m/H] approximate to 0.16) second generation stars are also enhanced in helium by small amount (Delta Y approximate to 0.03) and younger by similar to 1.5 Gyr. The RGB split in the hk index is most likely indicating that the second generation stars were affected by supernovae enrichment, together with the pollution of lighter elements by intermediate-mass asymptotic giant branch stars or fast-rotating massive stars. In order to confirm this, however, spectroscopy of stars in the two distinct RGB groups is urgently required.
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