Discovery of a Substellar Companion to the K2 III Giant ι Draconis
Discovery of a Substellar Companion to the K2 III Giant ι Draconis
复制标题
DOI：
10.1086/341629
复制
发表时间：
2002-09
期刊：
影响因子：
--
通讯作者：
S. Frink;D. Mitchell;A. Quirrenbach
中科院分区：
文献类型：
--
作者：
S. Frink;D. Mitchell;A. Quirrenbach
我们报告了在利克天文台进行的 K 巨星 ι Dra（HD 137759、HR 5744、HIP 75458）的精确径向速度测量，这揭示了围绕主星运行的亚星伴星的存在。对数据进行开普勒拟合得出轨道周期约为 536 天，偏心率为 0.70。假设 ι Dra 的质量为 1.05 M☉，则质量函数意味着最小伴星质量 m2 sin i 为 8.9 MJ，使其成为候选行星。相应的长半轴是1.3 AU。依巴谷未能探测到轨道运动，这使我们能够将伴星质量的上限设定为 45 MJ，从而确定该物体的亚恒星性质。我们估计，由于巨星的直径较大，该系统中的凌日可能已经在倾角低至 81°5 的情况下发生。 ι Dra 的伴星是第一颗被发现围绕巨星而不是主序星运行的褐矮星或行星。
We report precise radial velocity measurements of the K giant ι Dra (HD 137759, HR 5744, HIP 75458), carried out at Lick Observatory, which reveal the presence of a substellar companion orbiting the primary star. A Keplerian fit to the data yields an orbital period of about 536 days and an eccentricity of 0.70. Assuming a mass of 1.05 M☉ for ι Dra, the mass function implies a minimum companion mass m2 sin i of 8.9 MJ, making it a planet candidate. The corresponding semimajor axis is 1.3 AU. The nondetection of the orbital motion by Hipparcos allows us to place an upper limit of 45 MJ on the companion mass, establishing the substellar nature of the object. We estimate that transits in this system could occur already for inclinations as low as 81.°5, as a result of the large diameter of the giant star. The companion to ι Dra is the first brown dwarf or planet found to orbit a giant rather than a main-sequence star.