在我们正在进行的在Chamaeleon恒星形成区的金牛座T星周围的近距离和微弱的同伴的搜索中，我们最近（Schmidt et al 2008 b）提出了对年轻的金牛座T星和Chamaeleon成员CT Cha的新的共同自行伴星的直接观测和积分场光谱，并讨论了它与其他年轻的低质量物体和来自不同起源的合成模型光谱的比较。2008年2月，我们在欧洲南方天文台（ESO）的甚大望远镜（VLT）上使用自适应光学（AO）仪器Naos-Conica（NACO）首次获得了对伴星CT Cha b和另一个位于CT Cha东北约1.9角秒的微弱伴星（cc 2）的直接H波段观测。从这些数据中，我们现在可以通过4.4和4.8 sigma排除CT Cha b是一个不移动的背景物体，并发现cc 2很可能是一颗光谱型<= K4的背景星，自行为mu{alpha} cos{delta} = -8.5 +/- 5.7 mas/yr和mu{delta} = 12.0 +/- 5.6 mas/yr，与Cha I恒星形成区的成员不符。
英文摘要：
In our ongoing search for close and faint companions around T Tauri stars in the Chamaeleon star-forming region, we recently (Schmidt et al 2008b) presented direct observations and integral field spectroscopy of a new common proper motion companion to the young T-Tauri star and Chamaeleon member CT Cha and discussed its properties in comparison to other young, low-mass objects and to synthetic model spectra from different origins. We now obtained for the first time direct H-Band observations of the companion CT Cha b and of another faint companion candidate (cc2) approximately 1.9 arcsec northeast of CT Cha using the Adaptive Optics (AO) instrument Naos-Conica (NACO) at the Very Large Telescope (VLT) of the European Southern Observatory (ESO) in February 2008.
From these data we can now exclude by 4.4 & 4.8 sigma that CT Cha b is a non-moving background object and find cc2 to be most likely a background star of spectral type <= K4 with a proper motion of mu{alpha} cos{delta} = -8.5 +/- 5.7 mas/yr and mu{delta} = 12.0 +/- 5.6 mas/yr, not consistent with being a member of the Cha I star-forming region.
Parallaxes, Proper Motions, and Near-Infrared Photometry for 173 L and T Dwarfs From The US Naval Observatory Infrared Astrometry Program
United States Naval Observatory（美国海军天文台）；Flagstaff Dark Skies Coalition（弗拉格斯塔夫黑暗天空联盟）；L-3 Communications/Brashear（L-3通信/布莱尔）；Gemini Observatory/NSF’s NOIRLab（吉米尼天文台/美国国家科学基金会NOIR实验室）；California Institute of Technology (IPAC)（加州理工学院（IPAC））；Center for Astrophysics and Space Science, University of California San Diego（加州大学圣地亚哥分校天体物理与空间科学中心）
Jointly Modeling Roman Coronagraph Astrometry and Photometry Improves Orbital Parameter Estimates
Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University（西北大学跨学科天体物理探索与研究中心）；Department of Physics and Engineering, University of St. Thomas（圣托马斯大学物理与工程系）；Department of Astronomy and Astrophysics, University of California, Santa Cruz（加州大学圣克鲁斯分校天文与天体物理系）
Using Astrometry to Break Degeneracies in Stellar Surface Mapping
Michigan Institute for Data Science, University of Michigan（密歇根大学数据科学研究所）；Department of Astronomy, University of Michigan（密歇根大学天文学系）；Department of Electrical Engineering and Computer Science, University of Michigan（密歇根大学电气与计算机工程系）
