A DOUBLE MAIN SEQUENCE IN THE GLOBULAR CLUSTER NGC 6397
- Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife, Canary Islands (Spain)
- Max Planck Institute for Astrophysics, Postfach 1317, D-85741 Garching (Germany)
- Dipartimento di Astronomia, Universita di Padova, Vicolo dell'Osservatorio 3, Padova I-35122 (Italy)
- Space Telescope Science Institute, 3800 San Martin Drive, Baltimore, MD 21218 (United States)
- INAF-Osservatorio Astronomico di Collurania, via Mentore Maggini, I-64100 Teramo (Italy)
High-precision multi-band Hubble Space Telescope (HST) photometry reveals that the main sequence of the globular cluster NGC 6397 splits into two components, containing {approx}30% and {approx}70% of the stars. This double sequence is consistent with the idea that the cluster hosts two stellar populations: (1) a primordial population that has a composition similar to field stars, containing {approx}30% of the stars, and (2) a second generation with enhanced sodium and nitrogen, depleted carbon and oxygen, and a slightly enhanced helium abundance ({Delta}Y {approx} 0.01). We examine the color difference between the two sequences across a variety of color baselines and find that the second sequence is anomalously faint in m{sub F336W}. Theoretical isochrones indicate that this could be due to NH depletion.
- OSTI ID:
- 22011990
- Journal Information:
- Astrophysical Journal, Vol. 745, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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