TWO DISTINCT RED GIANT BRANCHES IN THE GLOBULAR CLUSTER NGC 288
- Center for Galaxy Evolution Research and Department of Astronomy, Yonsei University, Seoul 120-749 (Korea, Republic of)
- Department of Astronomy and Space Science, Sejong University, Seoul 143-747 (Korea, Republic of)
We report the presence of two distinct red giant branches (RGBs) in the globular cluster NGC 288 from the narrowband calcium and Stroemgren 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] {approx} 0.16) second generation stars are also enhanced in helium by small amount ({Delta}Y {approx} 0.03) and younger by {approx}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.
- OSTI ID:
- 21562640
- Journal Information:
- Astrophysical Journal Letters, Vol. 733, Issue 2; Other Information: DOI: 10.1088/2041-8205/733/2/L45; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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