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Title: EXPLANATION OF A SPECIAL COLOR–MAGNITUDE DIAGRAM OF STAR CLUSTER NGC 1651 FROM DIFFERENT MODELS

Abstract

The color–magnitude diagram (CMD) of globular cluster NGC 1651 has special structures including a broad main sequence, an extended main sequence turn-off, and an extended red giant clump. The reason for such a special CMD remains unclear. In order to test the difference among the results from various stellar population assumptions, we study a high-quality CMD of NGC 1651 from the Hubble Space Telescope archive using eight kinds of models. Distance modulus, extinction, age ranges, star formation mode, fraction of binaries, and fraction of rotational stars are determined and then compared. The results show that stellar populations both with and without age spread can reproduce the special structure of the observed CMD. A composite population with extended star formation from 1.8 Gyrs ago to 1.4 Gyrs ago, which contains 50% binaries and 70% rotational stars, fits the observed CMD best. Meanwhile, a 1.5 Gyr-old simple population that consists of rotational stars can also fit the observed CMD well. The results of CMD fitting are shown to depend strongly on stellar population type (simple or composite), and fraction of rotators. If the member stars of NGC 1651 formed in a single star burst, the effect of stellar rotation should be very important formore » explaining the observed CMDs. Otherwise, the effect may be small. It is also possible that the special observed CMD is a result of the combined effects of stellar binarity, rotation, and age spread. Therefore, further work on stellar population type and fraction of rotational stars of intermediate-age clusters are necessary to understand their observed CMDs.« less

Authors:
; ;  [1]
  1. Institute for Astronomy and History of Science and Technology, Dali University, Dali 671003 (China)
Publication Date:
OSTI Identifier:
22522540
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 802; 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; COLOR; COMPARATIVE EVALUATIONS; DIAGRAMS; DISTANCE; MAIN SEQUENCE STARS; ROTATION; SPACE; STAR CLUSTERS; STAR EVOLUTION; TELESCOPES

Citation Formats

Li, Zhongmu, Mao, Caiyan, and Chen, Li, E-mail: zhongmu.li@gmail.com. EXPLANATION OF A SPECIAL COLOR–MAGNITUDE DIAGRAM OF STAR CLUSTER NGC 1651 FROM DIFFERENT MODELS. United States: N. p., 2015. Web. doi:10.1088/0004-637X/802/1/44.
Li, Zhongmu, Mao, Caiyan, & Chen, Li, E-mail: zhongmu.li@gmail.com. EXPLANATION OF A SPECIAL COLOR–MAGNITUDE DIAGRAM OF STAR CLUSTER NGC 1651 FROM DIFFERENT MODELS. United States. doi:10.1088/0004-637X/802/1/44.
Li, Zhongmu, Mao, Caiyan, and Chen, Li, E-mail: zhongmu.li@gmail.com. Fri . "EXPLANATION OF A SPECIAL COLOR–MAGNITUDE DIAGRAM OF STAR CLUSTER NGC 1651 FROM DIFFERENT MODELS". United States. doi:10.1088/0004-637X/802/1/44.
@article{osti_22522540,
title = {EXPLANATION OF A SPECIAL COLOR–MAGNITUDE DIAGRAM OF STAR CLUSTER NGC 1651 FROM DIFFERENT MODELS},
author = {Li, Zhongmu and Mao, Caiyan and Chen, Li, E-mail: zhongmu.li@gmail.com},
abstractNote = {The color–magnitude diagram (CMD) of globular cluster NGC 1651 has special structures including a broad main sequence, an extended main sequence turn-off, and an extended red giant clump. The reason for such a special CMD remains unclear. In order to test the difference among the results from various stellar population assumptions, we study a high-quality CMD of NGC 1651 from the Hubble Space Telescope archive using eight kinds of models. Distance modulus, extinction, age ranges, star formation mode, fraction of binaries, and fraction of rotational stars are determined and then compared. The results show that stellar populations both with and without age spread can reproduce the special structure of the observed CMD. A composite population with extended star formation from 1.8 Gyrs ago to 1.4 Gyrs ago, which contains 50% binaries and 70% rotational stars, fits the observed CMD best. Meanwhile, a 1.5 Gyr-old simple population that consists of rotational stars can also fit the observed CMD well. The results of CMD fitting are shown to depend strongly on stellar population type (simple or composite), and fraction of rotators. If the member stars of NGC 1651 formed in a single star burst, the effect of stellar rotation should be very important for explaining the observed CMDs. Otherwise, the effect may be small. It is also possible that the special observed CMD is a result of the combined effects of stellar binarity, rotation, and age spread. Therefore, further work on stellar population type and fraction of rotational stars of intermediate-age clusters are necessary to understand their observed CMDs.},
doi = {10.1088/0004-637X/802/1/44},
journal = {Astrophysical Journal},
number = 1,
volume = 802,
place = {United States},
year = {Fri Mar 20 00:00:00 EDT 2015},
month = {Fri Mar 20 00:00:00 EDT 2015}
}