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arXiv 1012.4232astro-ph.SR
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包含棕矮星2 MASS J0850359 +105716的宽、低质量多重系统的识别

Identification of a Wide, Low-Mass Multiple System Containing the Brown Dwarf 2MASS J0850359+105716

Jacqueline K. Faherty, Adam J. Burgasser, John J. Bochanski, Dagny L. Looper, Andrew A. West, Nicole S. van der Bliek

摘要:

我们发现NLTT 20346是紧双星(或三重双星)L矮星2 MASS J 0850359 +105716的一个M5+M6伴星系统。这附近(~31 pc),广泛分离(~7700 AU)的四元组系统是通过交叉匹配的自行目录。NLTT 20346的后续成像和光谱显示它是一个磁活性的M5+M6双星,其组成部分相距约2”(50-80 AU)。光学光谱的组件显示只有适度的H α发射对应的统计年龄为5 - 7 Gyr的两个M矮星。然而,NLTT 20346与XMM-牛顿源J085018.9+105644有关,根据X射线活动,NLTT 20346的年龄在2.5亿-4.5亿年之间。在2 MASS J 0850 +1057的光谱中的强Li吸收表明年龄上限为0.8 - 1.5 Gyr,有利于初级年龄的年轻化。使用演化模型结合采用的系统年龄0.25-1.5 Gyr表明,如果它是一个双星,2 MASS J 0850 +1057的总质量为0.07+/-0.02 Msun。NLTT 20346/2 MASS J 0850 +1057加入了越来越多的包含棕矮星双星的等级系统的列表,并且是该领域中发现的结合能最低的协会之一。通过对大质量扩展盘的引力碎裂进行的形成模拟已经成功地产生了这个系统的特定模拟。

英文摘要:

We report our discovery of NLTT 20346 as an M5+M6 companion system to the tight binary (or triple) L dwarf 2MASS J0850359+105716. This nearby (~31 pc), widely separated (~7700 AU) quadruple system was identified through a cross-match of proper motion catalogs. Follow-up imaging and spectroscopy of NLTT 20346 revealed it to be a magnetically active M5+M6 binary with components separated by ~2" (50-80 AU). Optical spectroscopy of the components show only moderate Halpha emission corresponding to a statistical age of ~5 - 7 Gyr for both M dwarfs. However NLTT 20346 is associated with the XMM-Newton source J085018.9+105644, and based on X-ray activity the age of NLTT 20346 is between 250-450 Myr. Strong Li absorption in the optical spectrum of 2MASS J0850+1057 indicates an upper age limit of 0.8 - 1.5 Gyr favoring the younger age for the primary. Using evolutionary models in combination with an adopted system age of 0.25-1.5 Gyr indicates a total mass for 2MASS J0850+1057 of 0.07+/-0.02 Msun if it is a binary. NLTT 20346/2MASS J0850+1057 joins a growing list of hierarchical systems containing brown dwarf binaries and is among the lowest binding energy associations found in the field. Formation simulations via gravitational fragmentation of massive extended disks have successfully produced a specific analog to this system.

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