EMPIRICAL ISOCHRONES FOR LOW MASS STARS IN NEARBY YOUNG ASSOCIATIONS
EMPIRICAL ISOCHRONES FOR LOW MASS STARS IN NEARBY YOUNG ASSOCIATIONS
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附近年轻星团中低质量恒星的经验等时线
DOI：
10.1088/0004-637x/808/1/23
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发表时间：
2015-05
影响因子：
4.9
通讯作者：
Herczeg GJ
中科院分区：
文献类型：
--
作者：
Herczeg Gregory J.;Hillenbr;Lynne A.;Herczeg GJ
年轻恒星的绝对年龄对于前主序星和拱星演化的许多问题都很重要，但长期以来一直被认为是难以推导和校准的。本文利用文献中的光谱类型和光度学方法，构造了η Cha星协、Tu Cha星协和TW Hya星协以及β Pic和Tuc-Hor移动群中低质量恒星和褐矮星的经验等时线。一个成功的主序星前演化理论应该与这些年轻恒星群的恒星轨迹形状相匹配。然而，当比较组合的经验等时线从演化模型预测的等时线，差异导致恒星年龄估计的光谱类型（质量）的依赖。改进处方对流和边界条件的最新模型的前主序演化导致显着改善经验和模型等时线之间的对应关系，在低温下的小偏移，可能是由观测的不确定性或模型的局限性。独立的模型预测，线性拟合结合这些地区的恒星轨迹提供了一个简单的经验方法来订购集群的光度与光谱类型的依赖减少。根据各种现代模型计算的β Pic移动星群的Li耗尽边界年龄也意味着上斯科OB星群的低质量成员的年龄为1.44亿年，这比最近估计的中质量和高质量成员的年龄1.1亿年要年轻。
Absolute ages of young stars are important for many issues in pre-main-sequence stellar and circumstellar evolution but long have been recognized as difficult to derive and calibrate. In this paper, we use literature spectral types and photometry to construct empirical isochrones in Hertzsprung–Russell diagrams for low mass stars and brown dwarfs in the η Cha, ϵ Cha, and TW Hya Associations and the β Pic and Tuc-Hor Moving Groups. A successful theory of pre-main-sequence evolution should match the shapes of the stellar loci for these groups of young stars. However, when comparing the combined empirical isochrones to isochrones predicted from evolutionary models, discrepancies lead to a spectral type (mass) dependence in stellar age estimates. Improved prescriptions for convection and boundary conditions in the latest models of pre-main-sequence evolution lead to a significantly improved correspondence between empirical and model isochrones, with small offsets at low temperatures that may be explained by observational uncertainties or by model limitations. Independent of model predictions, linear fits to combined stellar loci of these regions provide a simple empirical method to order clusters by luminosity with a reduced dependence on spectral type. Age estimates calculated from various sets of modern models that reproduce Li depletion boundary ages of the β Pic Moving Group also imply a ∼4 Myr age for the low mass members of the Upper Sco OB Association, which is younger than the 11 Myr age that has been recently estimated for intermediate and high mass members.
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影响因子：
4.8
作者：
A. Binks;R. Jeffries
通讯作者：
A. Binks;R. Jeffries
DOI：
10.1111/j.1365-2966.2011.19945.x
发表时间：
2011-10
影响因子：
4.8
作者：
M. Gennaro;P. Moroni;Emanuele Tognelli Max-Planck-Institut fuer Astronomie-Emanuele-Tognelli-Max-Planck-Institut-fuer-102218120;Heidelberg;U. Pisa;I. N. D. F. N. S. Pisa-I.-N.-D.-F.-N.-S.-Pisa-102489794
通讯作者：
M. Gennaro;P. Moroni;Emanuele Tognelli Max-Planck-Institut fuer Astronomie-Emanuele-Tognelli-Max-Planck-Institut-fuer-102218120;Heidelberg;U. Pisa;I. N. D. F. N. S. Pisa-I.-N.-D.-F.-N.-S.-Pisa-102489794
DOI：
10.1088/0004-637x/698/1/660
发表时间：
2009-05
期刊：
The Astrophysical Journal
影响因子：
--
作者：
T. Laskar;D. Soderblom;J. A. Valenti;John R. Stauffer
通讯作者：
T. Laskar;D. Soderblom;J. A. Valenti;John R. Stauffer
DOI：
10.1088/0004-637x/758/1/31
发表时间：
2012-09
期刊：
The Astrophysical Journal
影响因子：
--
作者：
K. Luhman;E. Mamajek
通讯作者：
K. Luhman;E. Mamajek
DOI：
10.1088/0004-637x/771/2/129
发表时间：
2013-05
期刊：
The Astrophysical Journal
影响因子：
--
作者：
S. Andrews;K. Rosenfeld;A. Kraus;D. Wilner
通讯作者：
S. Andrews;K. Rosenfeld;A. Kraus;D. Wilner