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Title: A DOUBLE MAIN SEQUENCE IN THE GLOBULAR CLUSTER NGC 6397

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.
Authors:
;  [1] ;  [2] ;  [3] ; ;  [4] ;  [5] ;  [6]
  1. Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife, Canary Islands (Spain)
  2. Max Planck Institute for Astrophysics, Postfach 1317, D-85741 Garching (Germany)
  3. Dipartimento di Astronomia, Universita di Padova, Vicolo dell'Osservatorio 3, Padova I-35122 (Italy)
  4. Space Telescope Science Institute, 3800 San Martin Drive, Baltimore, MD 21218 (United States)
  5. INAF-Osservatorio Astronomico di Collurania, via Mentore Maggini, I-64100 Teramo (Italy)
  6. Division of Astronomy and Astrophysics, University of California, Los Angeles, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States)
Publication Date:
OSTI Identifier:
22011990
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 745; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; CARBON; COLOR; HELIUM; NITROGEN; OXYGEN; PHOTOMETRY; SODIUM; STARS; TELESCOPES