THE TRENDS HIGH-CONTRAST IMAGING SURVEY. VI. DISCOVERY OF A MASS, AGE, AND METALLICITY BENCHMARK BROWN DWARF
THE TRENDS HIGH-CONTRAST IMAGING SURVEY. VI. DISCOVERY OF A MASS, AGE, AND METALLICITY BENCHMARK BROWN DWARF
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高对比度成像趋势调查。
DOI：
10.3847/0004-637x/831/2/136
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
H. Isaacson
中科院分区：
文献类型：
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作者：
J. Crepp;E. Gonzales;Eric B. Bechter;B. Montet;J. Johnson;D. Piskorz;A. Howard;H. Isaacson
亚恒星天体的质量和年龄是退化参数，在没有额外信息的情况下，使褐矮星的演化状态变得模糊不清。理论模型通常用于帮助区分年老的大质量棕矮星和年轻的低质量棕矮星，但这些模型尚未得到适当的校准。我们已经开展了一项红外高对比度成像计划，目标是探测作为附近恒星同伴的亚恒星物体，以帮助打破推断的物理性质（如质量，年龄和成分）的简并。而不是单独使用成像观测，我们的目标是预先选择的基础上存在的动态加速度从多年的恒星径向速度（RV）测量。在这篇论文中，我们发现了一颗罕见的基准褐矮星，它绕着附近的太阳型（G9 V）星星HD 4747（[Fe/H]=-0.22 ±0.04）运行，轨道距离仅为ρ = 11.3 ± 0.2 Au（θ = 0."6）。18年来进行的精确多普勒测量揭示了伴星的轨道，并使我们能够使用动力学对其质量进行强有力的限制。相对测光（Δ Ks = 9.05 ± 0.14，，）表明HD 4747 B很可能是一颗晚型L矮星，如果靠近L/T转换，则是研究云物理、变率和偏振的有趣来源。我们估计一个依赖于模型的质量为年龄的陀螺仪的基础上gyrochronology。结合天体测量和RV数据，我们直接计算了伴星的动力学质量和轨道（e = 0.740 ± 0.002）。作为一个新的质量、年龄和金属丰度基准，HD 4747 B将作为精确天体物理学的实验室，测试描述棕矮星出射辐射的理论模型。
The mass and age of substellar objects are degenerate parameters leaving the evolutionary state of brown dwarfs ambiguous without additional information. Theoretical models are normally used to help distinguish between old, massive brown dwarfs and young, low-mass brown dwarfs but these models have yet to be properly calibrated. We have carried out an infrared high-contrast imaging program with the goal of detecting substellar objects as companions to nearby stars to help break degeneracies in inferred physical properties such as mass, age, and composition. Rather than using imaging observations alone, our targets are pre-selected based on the existence of dynamical accelerations informed from years of stellar radial velocity (RV) measurements. In this paper, we present the discovery of a rare benchmark brown dwarf orbiting the nearby (d = 18.69 ± 0.19 pc), solar-type (G9V) star HD 4747 ([Fe/H] = −0.22 ± 0.04) with a projected separation of only ρ = 11.3 ± 0.2 au (θ = 0.″6). Precise Doppler measurements taken over 18 years reveal the companion’s orbit and allow us to place strong constraints on its mass using dynamics ( ). Relative photometry (ΔKs = 9.05 ± 0.14, , ) indicates that HD 4747 B is most likely a late-type L-dwarf and, if near the L/T transition, an intriguing source for studying cloud physics, variability, and polarization. We estimate a model-dependent mass of for an age of Gyr based on gyrochronology. Combining astrometric measurements with RV data, we calculate the companion dynamical mass ( ) and orbit (e = 0.740 ± 0.002) directly. As a new mass, age, and metallicity benchmark, HD 4747 B will serve as a laboratory for precision astrophysics to test theoretical models that describe the emergent radiation of brown dwarfs.