We present a high-precision infrared radial velocity (RV) study of late-type stars using spectra obtained with NIRSPEC at the W. M. Keck Observatory. RV precisions of 50?m?s–1 are achieved for old field mid-M dwarfs using telluric features for wavelength calibration. Using this technique, 20 young stars in the β Pic (age ~ 12?Myr) and TW Hya (age ~ 8?Myr) Associations were monitored over several years to search for low-mass companions; we also included the chromospherically active field star GJ 873 (EV Lac) in this survey. Based on comparisons with previous optical observations of these young active stars, RV measurements at infrared wavelengths mitigate the RV noise caused by star spots by a factor of ~3. Nevertheless, star spot noise is still the dominant source of measurement error for young stars at 2.3 μm, and limits the precision to ~77?m?s–1 for the slowest rotating stars (v sin i 6?km?s–1), increasing to ~168?m?s–1 for rapidly rotating stars (v sin i 12?km?s–1). The observations reveal both GJ 3305 and TWA 23 to be single-lined spectroscopic binaries; in the case of GJ 3305, the motion is likely caused by its 009 companion, identified after this survey began. The large amplitude, short-timescale variations of TWA 13A are indicative of a hot Jupiter-like companion, but the available data are insufficient to confirm this. We label it as a candidate RV variable. For the remainder of the sample, these observations exclude the presence of any "hot" (P 3?days) companions more massive than 8 M Jup and any "warm" (P 30?days) companions more massive than 17?M Jup, on average. Assuming an edge-on orbit for the edge-on disk system AU Mic, these observations exclude the presence of any hot Jupiters more massive than 1.8?M Jup or warm Jupiters more massive than 3.9?M Jup.
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机译：我们使用W.M.凯克天文台的NIRSPEC获得的光谱，对晚型恒星进行高精度红外径向速度（RV）研究。使用中空特征进行波长校准，对于中场中型小矮星，RV精度达到50？m？s-1。使用这项技术，对βPic（年龄约12？Myr）和TW Hya（年龄约8？Myr）协会中的20个年轻恒星进行了几年的监测，以寻找低质量的同伴。在这次调查中，我们还将色球活动场星GJ 873（EV Lac）包括在内。根据与这些年轻活跃恒星先前的光学观测结果的比较，红外波长下的RV测量将星点引起的RV噪声降低了约3倍。尽管如此，对于2.3μm的年轻恒星，星点噪声仍然是测量误差的主要来源，并且对于旋转最慢的恒星（v sin i <6？km？s–1），其精度限制在〜77？m？s–1。 ），对于快速旋转的恒星（v sin i> 12？km？s–1）增加到〜168？m？s–1。观测结果表明，GJ 3305和TWA 23均为单线光谱二进制文件。对于GJ 3305，该运动很可能是由其009伴侣引起的，该伴侣是在此调查开始后确定的。 TWA 13A的大幅度，短时标变化表明是类似木星的伴星，但可用数据不足以证实这一点。我们将其标记为RV候选变量。对于样本的其余部分，这些观察结果排除了质量大于8 M Jup的任何“热”（P <3天）同伴和质量大于17μM的任何“热”（P <30天）同伴的存在。朱普，平均而言。假定边缘磁盘系统AU Mic处于边缘轨道，这些观察结果排除了存在质量大于1.8？M Jup的热木星或质量大于3.9？M Jup的热木星。
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