发现18个木星质量的RV伴星绕着褐矮星候选者ChaHa8运行
Discovery of 18 Jupiter mass RV companion orbiting the brown dwarf candidate ChaHa8
摘要：
我们报告发现一个16-20木星质量的径向速度同伴周围非常年轻（3百万年）的褐矮星候选人ChaHa 8。根据2000年至2007年期间在VLT使用UVES拍摄的ChaHa 8的高分辨率阶梯光谱，通过RV可变性以1.6 km/s的半振幅检测到伴星。开普勒拟合的数据得出伴星的轨道周期为1590天，离心率为e=0.49。一个同伴的最小质量M2 sin我之间的16和20木星质量时，使用模型相关的质量估计的主要推导出来。质量比M2/M1可能小至0.2，并且以87%的概率小于0.4。ChaHa 8肯定是迄今为止在褐矮星或极低质量恒星附近的近轨道（约1 AU）中发现的质量最低的伴星。从轨道解的不确定性来看，不能完全排除伴星有行星质量的可能性。无论如何，它的发现都是朝着探测BDs周围的RV行星迈出的重要一步。此外，ChaHa 8是第四个已知的光谱褐矮星或非常低质量的双星系统，具有RV轨道解，也是第二个已知的非常年轻的系统。
英文摘要：
We report the discovery of a 16-20 Jupiter mass radial velocity companion around the very young (3 Myr) brown dwarf candidate ChaHa8. Based on high-resolution echelle spectra of ChaHa8 taken between 2000 and 2007 with UVES at the VLT, a companion was detected through RV variability with a semi-amplitude of 1.6 km/s. A Kepler fit to the data yields an orbital period of the companion of 1590 days and an eccentricity of e=0.49. A companion minimum mass M2sin i between 16 and 20 Jupiter masses is derived when using model-dependent mass estimates for the primary. The mass ratio M2/M1 might be as small as 0.2 and, with a probability of 87%, it is less than 0.4. ChaHa8 harbors most certainly the lowest mass companion detected so far in a close (~1 AU) orbit around a brown dwarf or very low-mass star. From the uncertainty in the orbit solution, it cannot completely be ruled out that the companion has a mass in the planetary regime. Its discovery is in any case an important step towards RV planet detections around BDs. Further, ChaHa8 is the fourth known spectroscopic brown dwarf or very low-mass binary system with an RV orbit solution and the second known very young one.
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