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A DOUBLE MAIN SEQUENCE IN THE GLOBULAR CLUSTER NGC 6397
被引:90
|作者:
Milone, A. P.
[1
,2
]
Marino, A. F.
[3
]
Piotto, G.
[4
,5
]
Bedin, L. R.
[6
]
Anderson, J.
[6
]
Aparicio, A.
[1
,2
]
Cassisi, S.
[7
]
Rich, R. M.
[8
]
机构:
[1] Inst Astrofis Canarias, E-38200 San Cristobal la Laguna, Tenerife, Spain
[2] Univ La Laguna, Dept Astrophys, E-38200 San Cristobal la Laguna, Tenerife, Spain
[3] Max Planck Inst Astrophys, D-85741 Garching, Germany
[4] Univ Padua, Dipartimento Astron, I-35122 Padua, Italy
[5] INAF Osservatorio Astron Padova, I-35122 Padua, Italy
[6] Space Telescope Sci Inst, Baltimore, MD 21218 USA
[7] INAF Osservatorio Astron Collurania, I-64100 Teramo, Italy
[8] Univ Calif Los Angeles, Div Astron & Astrophys, Los Angeles, CA 90095 USA
关键词:
globular clusters: individual (NGC 6397);
stars: Population II;
MULTIPLE STELLAR POPULATIONS;
ADVANCED CAMERA;
OMEGA-CENTAURI;
GIANT STARS;
ACS SURVEY;
ABUNDANCES;
NGC-6397;
BRANCH;
ASTROMETRY;
NGC-2808;
D O I:
10.1088/0004-637X/745/1/27
中图分类号:
P1 [天文学];
学科分类号:
0704 ;
摘要:
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 similar to 30% and similar to 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 similar to 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 similar to 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(F336W). Theoretical isochrones indicate that this could be due to NH depletion.
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