The white dwarf population of NGC 6397

被引:29
作者
Torres, Santiago [1 ,2 ]
Garcia-Berro, Enrique [1 ,2 ]
Althaus, Leandro G. [3 ,4 ]
Camisassa, Maria E. [3 ,4 ]
机构
[1] Univ Politecn Cataluna, Dept Fis Aplicada, Castelldefels 08860, Spain
[2] Inst Space Studies Catalonia, Barcelona 08034, Spain
[3] Univ Nacl La Plata, Fac Ciencias Astron & Geofis, RA-1900 La Plata, Argentina
[4] Univ Nacl La Plata, CONICET, Inst Astrofis La Plata, RA-1900 La Plata, Argentina
来源
ASTRONOMY & ASTROPHYSICS | 2015年 / 581卷
关键词
globular clusters: individual: NGC 6397; stars: luminosity function; mass function; globular clusters: general; white dwarfs; MONTE-CARLO SIMULATIONS; GLOBULAR-CLUSTER NGC-6397; COLOR-MAGNITUDE DIAGRAM; FINAL MASS RELATIONSHIP; DEEP ADVANCED CAMERA; COOLING SEQUENCE; LUMINOSITY FUNCTION; MAIN-SEQUENCE; STELLAR EVOLUTION; OMEGA-CENTAURI;
D O I
10.1051/0004-6361/201526157
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Context. NGC 6397 is one of the most interesting, well-observed, and most thoroughly theoretically studied globular clusters. The existing wealth of observations allows us to study the reliability of the theoretical white dwarf cooling sequences of low-metallicity progenitors, to determine the age of NGC 6397 and the percentage of unresolved binaries. We also assess other important characteristics of the cluster, such as the slope of the initial mass function or the fraction of white dwarfs with hydrogen-deficient atmospheres. Aims. We present a population synthesis study of the white dwarf population of NGC 6397. In particular, we study the shape of the color-magnitude diagram and the corresponding magnitude and color distributions. Methods. To do this, we used an advanced Monte Carlo code that incorporates the most recent and reliable cooling sequences and an accurate modeling of the observational biases. Results. Our theoretical models and the observed data agree well. In particular, we find that this agreement is best for those cooling sequences that take into account residual hydrogen burning. This result has important consequences for the evolution of progenitor stars during the thermally pulsing asymptotic giant branch phase, since it implies that appreciable third dredge-up in low-mass, low-metallicity progenitors is not expected to occur. Using a standard burst duration of 1.0 Gyr, we obtain that the age of the cluster is 12.8(-0.75)(+0.50) Gyr. Greater ages are also compatible with the observed data, but then unrealistic longer durations of the initial burst of star formation are needed to fit the luminosity function. Conclusions. We conclude that a correct modeling of the white dwarf population of globular clusters, used in combination with the number counts of main-sequence stars, provides a unique tool for modeling the properties of globular clusters.
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页数:9
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