用Keck Laser导星自适应光学发现高度不等质量的双星T矮星:亚恒星理论模型和有效温度的共等性检验
Discovery of a Highly Unequal-Mass Binary T Dwarf with Keck Laser Guide Star Adaptive Optics: A Coevality Test of Substellar Theoretical Models and Effective Temperatures
摘要:
(节略)在野外棕矮星中,质量比高度不等的双星是很罕见的,已知的统计数据是q^(4.9+/-0.7)。然而,这样的系统可以测试的联合精度的演变和大气模型,在coevality的约束下(“等时线测试”)。我们使用目前已知的两个最极端的亚星双星,T1+T6 \eps Ind Bab双星和新发现的0.14”T2.0+T7.5双星,2 MASS 1209- 10 AB进行了这项测试。根据H-R图上各组分的位置,模型成功地表明这些系统是同时代的,内部年龄差分别为log(年龄)= 0.5{+0.4}{-0.3}和-0.8+/-1.3 dex。然而,从H-R图推导出的\eps Ind Bab的总质量(~80 Mjup)与报道的动力学质量不一致。这个问题,这是独立的假设年龄的系统,可以解释为一个~50-100 K的系统误差,在模型大气拟合;使两个质量测定一致导致推断年龄~6 Gyr的\eps Ind系统,比以前假设的。总的来说,这里研究的两个T矮星双星,以及最近在年龄和质量基准系统中T矮星的结果,在演化模型和/或模型大气中产生小(~100 K)误差的证据,但不是显着更大。最后,2 MASS 1209-10AB的二进制性质降低了其作为主要T3近红外光谱分型标准的实用性;我们建议SDSS 1206+28作为替代品。
英文摘要:
(Abridged) Highly unequal-mass ratio binaries are rare among field brown dwarfs, with the known census described by q^(4.9+/-0.7). However, such systems can test the joint accuracy of evolutionary and atmospheric models, under the constraint of coevality (the "isochrone test''). We carry out this test using two of the most extreme field substellar binaries currently known, the T1+T6 \eps Ind Bab binary and a newly discovered 0.14" T2.0+T7.5 binary, 2MASS 1209-10AB. Based on the locations of the components on the H-R diagram, models successfully indicate that the systems are coeval, with internal age differences of log(age) = 0.5{+0.4}{-0.3} and -0.8+/-1.3 dex, respectively. However, the total mass of \eps Ind Bab derived from the H-R diagram (~80 Mjup) is discrepant with the reported dynamical mass. This problem, which is independent of the assumed age of the system, can be explained by a ~50-100 K systematic error in the model atmosphere fitting; bringing the two mass determinations into consistency leads to an inferred age of ~6 Gyr for the \eps Ind system, older than previously assumed. Overall, the two T dwarf binaries studied here, along with recent results from T dwarfs in age and mass benchmark systems, yield evidence for small (~100 K) errors in the evolutionary models and/or model atmospheres, but not significantly larger. Finally, the binary nature of 2MASS 1209-10AB reduces its utility as the primary T3 near-IR spectral typing standard; we suggest SDSS 1206+28 as a replacement.
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