Young Low-Mass Stars and Brown Dwarfs in IC 348
Young Low-Mass Stars and Brown Dwarfs in IC 348
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DOI：
10.1086/307902
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发表时间：
1999-05
期刊：
影响因子：
--
通讯作者：
K. Luhman;K. Luhman
中科院分区：
文献类型：
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作者：
K. Luhman;K. Luhman
我提出了新的结果，从一个持续的计划，以确定和描述低质量的恒星和亚恒星的人口在年轻的集群IC 348（0.5-10百万年）。光学光谱学揭示了光谱类型晚至M8.25的年轻天体。这些源的本征J-H和H-K色是类矮星色，而R-I和I-J色则介于矮星和巨星的颜色之间。此外，从6500到9500焦耳的光谱与标准矮光谱和标准巨星光谱的平均值很好地再现，这表明这种平均值应该用于年轻晚型源的分类。绘制了IC 348（K6-M8）低质量粒子数的H-R图。年轻的四元组系统GG Tau（白色等人）的可能的同时代成分。和IC 348中的恒星轨迹作为经验等时线来检验理论演化模型。伯罗斯等人的计算似乎与恒星演化最早阶段的数据不一致。有公平的协议之间的数据和模型等时线的D 'Antona和Mazzitelli，除了附近的氢燃烧的限制。不能通过改变光谱类型和有效温度之间的转换来改善一致性。另一方面，对于Baraffe等人的模型，在后来的M型（介于矮星和巨星之间）中，温度尺度的调整使温度逐渐升高，使GG Tau的所有成分都处于同一模型等时线上，并使IC 348的人口具有恒定的年龄和年龄分布作为质量的函数。当考虑其他观测约束时，如GM Aur，DM Tau和GG Tau A的动力学质量，Baraffe等人的模型与年轻系统的观测最一致。在相容的温标下，D 'Antona & Mazzitelli和Baraffe等人的模型都认为氢燃烧的质量极限发生在M6附近，年龄为1000万年。因此，在对IC 348的研究中发现了几颗可能的棕矮星，质量低至20-30 MJ。
I present new results from a continuing program to identify and characterize the low-mass stellar and substellar populations in the young cluster IC 348 (0.5-10 Myr). Optical spectroscopy has revealed young objects with spectral types as late as M8.25. The intrinsic J-H and H-K colors of these sources are dwarflike, whereas the R-I and I-J colors appear intermediate between the colors of dwarfs and giants. Furthermore, the spectra from 6500 to 9500 Å are reproduced well with averages of standard dwarf and giant spectra, suggesting that such averages should be used in the classification of young late-type sources. An H-R diagram is constructed for the low-mass population in IC 348 (K6-M8). The presumably coeval components of the young quadruple system GG Tau (White et al.) and the locus of stars in IC 348 are used as empirical isochrones to test the theoretical evolutionary models. The calculations of Burrows et al. do not appear to be consistent with the data at these earliest stages of stellar evolution. There is fair agreement between the data and the model isochrones of D'Antona & Mazzitelli, except near the hydrogen-burning limit. The agreement cannot be improved by changing the conversion between spectral types and effective temperatures. On the other hand, for the models of Baraffe et al., an adjustment of the temperature scale to progressively warmer temperatures at later M types, intermediate between dwarfs and giants, brings all components of GG Tau onto the same model isochrone and gives the population of IC 348 a constant age and age spread as a function of mass. When other observational constraints are considered, such as the dynamical masses of GM Aur, DM Tau, and GG Tau A, the models of Baraffe et al. are the most consistent with observations of young systems. With compatible temperature scales, the models of both D'Antona & Mazzitelli and Baraffe et al. suggest that the hydrogen-burning mass limit occurs near M6 at ages of ≲10 Myr. Thus, several likely brown dwarfs are discovered in this study of IC 348, with masses down to ~20-30 MJ.