Space Velocities of L- and T-Type Dwarfs
Space Velocities of L- and T-Type Dwarfs
复制标题
L型和T型矮星的空速
DOI：
10.1086/520673
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
R. Wainscoat
中科院分区：
文献类型：
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作者：
M. Z. Osorio;Eric Martin;Eric Martin;V. Béjar;H. Bouy;H. Bouy;R. Deshpande;R. Wainscoat
我们利用NIRSPEC和Keck II望远镜获得的高分辨率近红外光谱，获得了18个超冷矮星（M6.5-T8）样本的径向速度。我们已经确认Gl 570D的视向速度与k型主星Gl 570A的视向速度一致，从而为它们真正的伴侣关系提供了额外的支持。利用在4.37年的时间内获得的五次NIRSPEC径向速度测量数据，我们分析了2MASS J05591914-1404488 （T4.5 V）周围行星质量伴星的存在。我们计算了距离太阳20%以内的21个L和T矮星的UVW空间运动。这一群显示了UVW的速度，很好地重叠了太阳到m型恒星在相同空间体积内的典型运动学。然而，L和T型矮星的平均银河系速度和切向速度似乎比G到M型恒星的速度要小。相当一部分（~40%）的超冷矮星位于毕宿星移动群（0.4-2 Gyr）附近，这与早期类型的恒星邻居发现的10%-12%形成鲜明对比。此外，L和T样品的UVW分量的分布以及银河系总速度和切向速度的分布比附近的G型、K型和m型恒星的分布窄，但与F型恒星的色散相似。这表明，在太阳附近，L型和t型超冷矮星（包括棕矮星）的人口在运动学上比太阳型到早期M型恒星年轻，年龄可能在0.5-4 Gyr之间。
We have obtained radial velocities of a sample of 18 ultracool dwarfs (M6.5-T8) using high-resolution, near-infrared spectra obtained with NIRSPEC and the Keck II telescope. We have confirmed that the radial velocity of Gl 570D is coincident with that of the K-type primary star Gl 570A, thus providing additional support for their true companionship. The presence of planetary-mass companions around 2MASS J05591914-1404488 (T4.5 V) has been analyzed using five NIRSPEC radial velocity measurements obtained over a period of 4.37 yr. We have computed UVW space motions for a total of 21 L and T dwarfs within 20 pc of the Sun. This population shows UVW velocities that nicely overlap the typical kinematics of solar to M-type stars within the same spatial volume. However, the mean Galactic and tangential velocities of the L and T dwarfs appear to be smaller than those of G to M stars. A significant fraction (~40%) of the ultracool dwarfs lie near the Hyades moving group (0.4-2 Gyr), which contrasts with the 10%-12% found for earlier type stellar neighbors. In addition, the distributions of the UVW components and the distributions of the total Galactic and tangential velocities derived for the L and T sample are narrower than those measured for nearby G-, K-, and M-type stars, but similar to the dispersions obtained for F stars. This suggests that, in the solar neighborhood, the population of L- and T-type ultracool dwarfs (including brown dwarfs) is kinematically younger than solar-type to early M stars, with likely ages in the interval 0.5-4 Gyr.